Production of rubbery isoolefin polymers

ABSTRACT

A substantially gel free C 4  to C 7  isoolefin homopolymer rubber, butyl copolymer rubber, halogenated butyl rubber (e.g., chlorinated or brominated), or mixtures thereof, comprising a molecular weight distribution such that the ratio of the moments of said molecular weight distribution, Mz/Mw, is equal to or exceeds 2.0, and that portion of said molecular weight distribution which is equal to and greater than 4 times the peak molecular weight, Mp, comprises greater than 8 percent of the total polymer species, and Mp is greater than about 250,000 and wherein said polymer species of molecular weight less than Mp are substantially branch free. Various means are disclosed for effecting the molecular weight distribution including blending of homopolymers and/or copolymers of appropriate molecular weight and molecular weight distribution and direct polymerization using a functional reagent to introduce branching. The rubber compositions are particularly useful in applications in which butyl or halogenated butyl rubber is used and where it is desired to obtain high green strength in combination with an increased rate of stress relaxation. Such polymers are particularly well suited for use in tire innerliner compositions.

This is a continuation of application Ser. No. 611,209, filed Nov. 9,1990, now abandoned, which is a Rule 60 division based on U.S. Ser. No.131,938 filed Dec. 11, 1987, now U.S. Pat. No. 5,071,913.

BACKGROUND OF THE INVENTION

This invention relates to a method of improving the processingproperties of isoolefinic homopolymers and copolymers, especially thosecommonly known as butyl rubber or isobutylene-isoprene copolymer rubber.The invention also relates to methods for producing such improvedprocessing polymers and the specific molecular criteria which must becontrolled in order to obtain these improved properties. The inventionparticularly relates to the achievement of improved processingproperties by means of controlled and specific modification of themolecular weight distribution of these polymers. The term "butyl rubber"as used in the specification and claims means copolymers of C₄ to C₇isoolefins and C₄ to C₁₄ conjugated dienes which comprise about 0.5 toabout 15 mole percent conjugated diene and about 85 to 99.5 mole percentisoolefin. Illustrative examples of the isoolefins which may be used inthe preparation of butyl rubber are isobutylene, 2-methyl-1-propene,3-methyl-1-butene, 4-methyl-1-pentene and beta-pinene. Illustrativeexamples of conjugated dienes which may be used in the preparation ofbutyl rubber are isoprene, butadiene, 2,3-dimethyl butadiene,piperylene, 2,5-dimethylhexa-2,4-diene, cyclopentadiene, cyclohexadieneand methylcyclopentadiene. The preparation of butyl rubber is describedin U.S. patent application No. 2,356,128 and is further described in anarticle by R. M. Thomas et al. in Ind. & Eng. Chem., vol. 32, pp. 1283et seq., Oct., 1940. Butyl rubber generally has a viscosity averagemolecular weight between about 100,000 to about 1,500,000, preferablyabout 250,000 to about 800,000 and a Wijs Iodine No. (INOPO) of about0.5 to 50, preferably 1 to 20 (for a description of the INOPO test, seeIndustrial and Engineering Chemistry, Vol. 17, p. 367, 1945).

The term isoolefin homopolymers as used herein is meant to encompassthose homopolymers of C₄ to C₇ isoolefins particularly polyisobutylene,which have a small degree of terminal unsaturation and certainelastomeric properties. The principal commercial forms of these butylrubber and isoolefin polymers such as isobutylene isoprene butyl rubberand polyisobutylene, are prepared in a low temperature cationicpolymerization process using Lewis acid type catalysts, typicallyaluminum chloride being employed. Ethyl aluminum dichloride and borontrifluoride are also considered useful in these processes. The processextensively used in industry employs methyl chloride as the diluent forthe reaction mixture at very low temperatures, that is less than minus90° C. Methyl chloride is typically employed for a variety of reasons,including the fact that it is a solvent for the monomers and aluminumchloride catalyst and a nonsolvent for the polymer product therebyresulting in a slurry. Also, methyl chloride has suitable freezing andboiling points to permit, respectively, low temperature polymerizationand effective separation from the polymer and unreacted monomers.However, it is also possible to conduct such polymerizations in adiluent which is a solvent for the polymer produced, e.g., pentane,hexane and heptane and mixtures of such solvents with one another orwith methyl chloride and/or methylene chloride. As will be describedlater, there are some advantages which can be obtained by conducting thepolymerization in solution under certain conditions relating to theparticular monomers and other reactants employed in the polymerization.

The slurry polymerization process in methyl chloride offers a number ofadditional advantages in that a polymer concentration of approximately30% by weight in the reaction mixture can be achieved, as opposed to theconcentration of only about 8% to 12% in solution polymerization. Also,an acceptable, relatively low viscosity of the polymerization mass isobtained enabling the heat of polymerization to be removed moreeffectively by heat exchange. Slurry polymerization processes in methylchloride are used in the production of high molecular weightpolyisobutylene and isobutylene-isoprene butyl rubber polymers.

U.S. Pat. Nos. 4,252,710, 4,358,560 and 4,474,924, each incorporatedherein by reference, disclose methods for stabilizing againstagglomeration the slurry polymerization product of the isoolefinhomopolymers or butyl rubber copolymers polymerized in a polarchlorinated hydrocarbon diluent such as methyl chloride, methylenechloride, vinyl chloride or ethyl chloride. The significant advance ofslurry stabilization disclosed in those patents is achieved by the useof a stabilizing agent being (i) a preformed copolymer having alyophilic, polymerization diluent soluble portion and a lyophobicpolymerization diluent insoluble portion, the lyophobic portion beingsoluble in or adsorbable by the product polymer and the stabilizingagent being capable of forming an adsorbed solubilized polymer coatingaround the precipitated isoolefin homopolymer or butyl copolymer tostabilize the slurry, or (ii) an in situ formed stabilizing agentcopolymer formed from a stabilizer precursor, the stabilizer precursorbeing a lyophilic polymer containing a functional group capable ofcopolymerizing or forming a chemical bond with the product polymer, thefunctional group being cationically active halogen or cationicallyactive unsaturation, the lyophobic portion of the stabilizing agentbeing product polymer, the stabilizing agent so formed being capable offorming an adsorbed solubilized polymer coating around the precipitatedproduct polymer to stabilize the product polymer slurry.

Various classes and specific types of useful stabilizing agents aredisclosed and exemplified, some of which produce substantially gel freepolymers and others of which produce gelled polymers under variouspolymerization conditions. Some of the stabilizing agents disclosed maybe useful herein under appropriate, defined conditions, but the criteriafor distinguishing between those which can be used herein and thosewhich cannot be used were not known or disclosed in those patents. Inaddition, in order to produce the desired polymer with improvedproperties as disclosed in the invention herein, the agents must be usedin effective concentration in order to produce controlled amounts ofdefined molecular weight components in the rubber; such criticallimitations were unknown in the prior art and were neither suggested norexemplified. Furthermore, alternative means for producing the unique,improved processing polymers of this invention are available as will befurther disclosed herein.

In the processing of the rubbers of commerce, it is preferred that theypossess sufficient green (uncured) strength to resist excessive flow anddeformation in the various handling operations. It is generally believedthat green strength is related to molecular weight with green strengthimproving as molecular weight increases. However, it is also desirablethat in certain applications such rubbers have a rapid stress relaxationrate so that the stresses imposed during forming operations relaxquickly and the rubber does not slowly change its shape or pull apartdue to these undissipated forming stresses. Unfortunately, stressrelaxation rate is also a function of molecular weight with therelaxation rate becoming slower as molecular weight increases. Hence, asmolecular weight is increased to improve green strength, stressrelaxation rate is reduced. Thus, as the rubber becomes better able toresist flow and deformation in the various handling operations itbecomes more prone to change shape or pull apart due to unrelaxedforming stresses and a compromise becomes necessary in which greenstrength is sacrificed in order to achieve sufficiently rapid stressrelaxation in the particular end use application. Furthermore,increasing molecular weight in order to increase green strength can makeit more difficult to process the polymer and to disperse fillers andadditives.

It would be desirable to be able to alter the balance between greenstrength and stress relaxation rate to achieve higher green strengthwithout sacrificing relaxation rate or faster relaxation rate withoutsacrificing green strength.

It has previously been disclosed that some processing properties ofnatural rubber can be improved by the addition of prevulcanized naturalrubber latex into natural rubber (see, e.g., U.S. Pat. Nos. 1,443,149and 1,682,857); such a product was commercialized in the early 1960's(see, e.g., W. G. Wren, Rubber Chemistry & Technology, 34,378,403[1961]). Similarly, the addition of a gel fraction for achievingprocessing advantages in styrene-butadiene rubber (SBR) has also beenreported (see, e.g., L. M. White, Ind. & Eng. Chem., 37, 770 [1945]);Crawford and Tiger, Ind. & Eng. Chem., 41,592 (1949). Other disclosureshave also been made relating to the use of SBR crosslinked with divinylbenzene (D. L. Schoene, Ind. & Eng. Chem., 38,1246 [1946]) and blends ofcrosslinked latex with uncrosslinked latex (O. W. Burke, Jr., BritishPatent 799,043). In each of these early developments, the benefitdisclosed was achieved by use of a crosslinked rubber fraction. Themeans of producing a controlled change in molecular weight distributionand the specific nature of the change required were not understood ordisclosed, nor was the specific application of such knowledge toisoolefin homopolymers and butyl rubber polymers.

As noted above, the use of divinyl benzene to effect crosslinking in arubber has been described. Other references have similarly disclosed theuse of divinyl benzene (DVB) in a butyl polymerization process to obtaina modified product with increased resistance to cold flow (U.S. Pat. No.2,781,334); the product is alternatively described as soluble in organicsolvents and having a relatively low gel content. U.S. Pat. No.3,135,721 is directed to a particular process which uses DVB forreducing fouling during start-up of the polymerization process and doesnot disclose properties for any product or distinguish between thoseproducts containing very low levels of DVB and those at higherconcentrations. Other references disclose the use of DVB at even higherconcentrations to produce polymers containing large amounts of gel andso are not particularly relevant to the invention herein (U.S. Pat. Nos.2,671,774; 2,729,626; 3,548,080). Finally, a polymerization processpatent (U.S. Pat. No. 3,219,641) discloses the use of DVB and highboiling equivalents in the range of 0.01 to 10 weight percent based ontotal polymer to clean a recycle monomer stream before drying.

Still other references disclose methods and products in whichcationically polymerizable monomers such as isobutylene are grafted tohalogenated polymers with reactive halogen such as chlorinated butylrubber, polyvinylchloride, etc. (U.S. Pat. Nos. 3,476,831; 3,904,708;and 3,933,942). The objective of these references is to produce acopolymer in which a monomer such as isobutylene (orisobutylene/isoprene) is grafted onto a diene polymer backbone which mayinclude styrene. However, the references are not directed to the butylrubber process, the grafted materials are not essentially butyl polymersas described herein and the method of obtaining butyl polymers with theimproved characteristics disclosed herein is not disclosed or suggested.Furthermore, the references are particularly limited with respect to thenature of the catalyst which can accomplish the grafting process, andethyl aluminum dichloride, a useful catalyst herein, is described asparticularly unsuitable for the purposes of these references (see, e.g.,U.S. Pat. No. 3,904,708, Example 16).

SUMMARY OF THE INVENTION

A composition of matter comprising C₄ to C₇ isoolefin homopolymerrubber, butyl copolymer rubber, halogenated butyl copolymer rubber ormixtures thereof, wherein the molecular weight distribution of therubber or the mixture is such that the ratio of the moments of themolecular weight distribution, Mz/Mw, is equal to or exceeds 2.0 andthat portion of the molecular weight distribution which is equal to andgreater than 4 times the peak molecular weight, Mp, comprises greaterthan 8 percent of the total polymer species and Mp is greater than about250,000 and wherein said polymer species of molecular weight less thanMp are substantially branch free. The desired molecular weightdistribution is achieved by blending of homopolymers and/or copolymersof appropriate molecular weight and molecular weight distribution and bydirect polymerization using a functional reagent to introduce branching.The rubbers are substantially gel free and have improved green strengthand stress relaxation rate which properties are particularlyadvantageous in applications in which butyl or halogenated butyl rubberis used and where it is desired to obtain high green strength incombination with an increased rate of stress relaxation. Such polymersare particularly well suited for use in tire innerliner and innertubecompositions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically depicts the relationship of green strength to 4minute relaxed stress for blends prepared according to the presentinvention and for commercially produced polymers.

FIGS. 2 and 3 illustrate GPC chromatograms of typical Butyl polymer anda polymer of the invention which contains a branched high ends mode.

FIG. 4 illustrates a UV trace of the latter inventive polymer.

FIGS. 5 and 6 depict the results of stress relaxation processabilitytesting of several polymers of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Polymerization of isoolefin homopolymer or butyl rubber copolymers,e.g., polyisobutylene and isobutyleneisoprene butyl rubber, are wellknown in the art, as noted above. Various grades of these polymers havebeen commercially available for many years, such products differing inmolecular weight and unsaturation (in the case of theisoprene-containing copolymer).

Processes used to produce these polymers include solution polymerizationutilizing diluents such as aliphatic hydrocarbons, such as pentane,hexane and heptane. Since polymerization is typically conducted at lowtemperatures, generally less than about -20° C., typically less thanabout -70° C., preferably less than about -90° C., the diluent must beselected with the operating temperature in mind in order to avoidfreezing. Alternative processes utilize the slurry polymerization methodwherein the diluent is initially a solvent for the monomers andcatalyst; upon polymerization the polymer forms a slurry in the diluent.Useful diluents for this purpose include methyl chloride, methylenechloride, vinyl chloride and ethyl chloride, with methyl chloride beingpreferred. Mixtures of diluents are also useful, including mixtures ofsolvent-type and slurry-type, for example hexane and methyl chloride.

Various techniques are available for modifying the molecular weightand/or molecular weight distribution of polyisoolefins such aspolyisobutylene and butyl rubber such as isobutylene-isoprene rubber.The invention herein is directed to achieving improvements in theproperties of green strength and stress relaxation of the polymer andcompositions in which it is used (e.g., inner tubes and tireinnerliners); improvements in tack can also be obtained. The desiredimprovements are achieved by modifying the molecular weight distributionin a specific manner and controlling the type and extent of branching inthe polymer as will be described in detail.

For the purposes of this disclosure properties have been determined asfollows:

I. Green Strength/stress Relaxation

A. Sample Preparation

Samples can be tested in the neat form (polymer only, typicallystabilized against oxidation) or in a compounded form containingspecific amounts and types of filler (e.g., carbon black), extender(e.g., rubber process oil), etc. For the test to be run in tension,tensile pads (6 in.×6 in.×0.080 in. thickness) are pressed betweensheets of Mylar film at a pressure of 1500 psi (12.4 MPa), appliedgradually over a period of 1.5 min. and molded at a temperature of 150°C. for 20 minutes. The mold is transferred to a water cooled press andcooled under pressure for 20 minutes. The molded pads are removed fromthe Mylar and placed between polyethylene sheets. Test specimens are cut0.5 in. wide×6 in. long; thickness is accurately measured.

B. Testing

Using a tensile testing machine such as an Instron® tester, a sample isextended to 100% elongation at 20 inches/minute; green strength isdefined as the peak stress at 100% elongation. The sample is held at100% extension and allowed to relax for 4 minutes; the relaxed stress at4 minutes is recorded. Stress values are expressed in psi using theinitial sample cross-sectional area.

C. Stress Relaxation Processability Tester (SRPT)

The SRPT test is an alternate means of evaluating green strength/stressrelaxation which measures the compressive stress relaxation of apolymeric sample. A small cylindrical sample (typically 0.5 inchdiameter and about 0.25 inch thick) is compressed in two steps. Thefirst step compresses the sample to a thickness of 4.5 mm and in asecond step the sample is compressed again to a thickness of 3 mm. Thefirst step is for conditioning and preheating the material. During thesecond compression step stress is monitored with time and a referencestress and a relaxation time are measured. The reference stress (inunits of psi) is the stress at a pre-set reference time after the secondcompression. The relaxation time is the time between the reference timeand the time at which the reference stress decays by a given percentage.The reference stress is a measure of the material's ability to resist aquick deformation (similar to a modulus) and the relaxation time is ameasure of the ability of the polymer molecules to relax from a stressedstate.

1. Sample Preparation

A. Molding

A disk of 1.25 inch diameter and 0.30 inch thick is compression moldedusing the following conditions:

Temperature--200° C. for non-halogenated polymers, 150° C. forhalogenated polymers or 100° C. for filled compositions.

Preheat sample with no pressure for two minutes.

Raise the force to 15 tons (for a 9 cavity disk mold) and hold thepressure constant for 2 minutes.

Remove the mold and place it in a water cooled press for 5 to 10 minutesunder a closing force of 15 tons.

B. SRPT Sample

Between two and three cylindrical samples are cut from the above diskusing a 1/2 inch die.

C. SRPT Measurements

Before the test is started, temperature equilibrium is established. Atest sample is placed at the center of the compression chamber and thetest sequence is started. After the stress resulting from the secondcompression stage has decayed to the pre-set extent, the referencestress and relaxation time are recorded. Typically, an extent of decayfrom the reference stress of 50% or 75% is used.

D. Normalization

Green strength and stress relaxation values obtained for variousmaterials can be normalized against a given material. This isaccomplished by dividing each resulting reference stress by thereference stress for the standard material. The normalization should bedone for measurements using idential parameters. However, afternormalization, materials measured with one or more changes in the testparameters can still be compared if the standard material is the samematerial and was measured with both sets of parameters. For example, ifthe extent of decay is 75 percent in one set of tests and 50 percent inanother set, both sets can be normalized against the same standard whichis itself measured under both conditions. Since decay follows anexponential form, a normalized relaxation time is not strongly dependenton the extent of decay.

II. Gel Permeation Chromatography (GPC) Molecular Weight

A comprehensive description of the theory and practice of the now wellknown GPC technique can be found in "Modern Size-Exclusion LiquidChromatography, Practice of Gel Permeation and Gel FiltrationChromatography" by W. W. Yau, J. J. Kirkland and D. D. Bly (John Wiley &Sons, 1979); further reference to this text will indicate the chapterand page of "GPC-Yau."

By way of generalization, GPC is an analytical procedure used forseparating molecules by differences in size. The procedure as applied topolymers results in a concentration distribution of molecular weights.Most often, concentration is determined using differential refractiveindex (DRI) and the concentration v. time elution curve is related tomolecular weight by means of a calibration curve based on a "known"standard. Utilizing low-angle laser light-scattering (LALLS) photometryin conjunction with DRI, direct determination of molecular weight can bemade (GPC-Yau, Chapter 5.12, page 156 ff). Furthermore, the LALLStechnique is more sensitive to, and more accurately determines very highmolecular weight portions of the distribution (e.g., 1,000,000 andhigher).

Molecular weight averages can be calculated based on the data obtainedfrom a GPC test (GPC-Yau, Chapter 1.3, page 4 ff). The most frequentlycited molecular weight averages are: number average (Mn), weight average(Mw) and Z-average (Mz). These averages are also referred to as thevarious moments of the distribution. For a monodispersed system (inwhich each molecule has the same molecular weight), the moments wouldequal one another, but for a polydisperse system Mz is greater than Mwwhich is greater than Mn. Higher molecular weight species have a greaterinfluence on the Z and weight averages whereas lower molecular weightspecies more greatly influence the number average. The breadth of thedistribution overall as well as parts of it can be characterized byreference to various ratios, e.g., Mw/Mn and Mz/Mw; the higher thevalues of the ratio, the broader the distribution of molecular weights.Furthermore, a multimodal distribution can be more accuratelycharacterized by reference to a ratio which incorporates that portion ofthe distribution reflecting the mode of interest. For example,comparison between a polymer with a large concentration of a highmolecular weight "tail" and the same polymer without such a tail wouldbe more accurately reflected in the Mz/Mw ratio.

When a distribution of molecular weight is present in a polymercomposition as a result of, e.g., the blending of two or more polymersor resulting directly from polymerization, such a distribution will haveat least one peak in a plot of molecular weight versus concentration.For the purposes of this invention, peak molecular weight, identified asMp, is that molecular weight corresponding to the maximum concentrationin the polymer concentration-elution time GPC trace (chromatogram).Since GPC instruments do not usually operate with a strictly linearcalibration relationship between the logarithm of molecular weight andelution time, such a maximum will be slightly displaced from the maximumin the differential weight distribution, dW(M)/d log M. For rigorouscomparison between different GPC instruments, it is necessary that thecalibration, log M versus time, be essentially linear in the region ofMp, but minor discrepancies do not detract from the basic advance of thepresent invention.

For the case of a chromatogram with multiple peaks (corresponding tomultiple compositional elements in the molecular weight distribution),Mp is identified as the molecular weight at the local maximum of themajor component of the molecular weight distribution in the original GPCchromatogram trace. In general, such a major component comprisessubstantially linear molecules. For the purpose of this invention Mpdoes not correspond to the high molecular weight component of thedistribution generated by the use of a branching agent duringpolymerization. Similarly, it does not correspond to the high or lowmolecular weight components blended to prepare a final polymercomposition.

Identification of the peak molecular weight (Mp) of the polymermolecular weight distribution is significant because another definedcharacteristic of the distribution is keyed to it; the high endsfraction. For the purposes of this invention the high ends fraction ofthe molecular weight distribution is characterized by GPC analysis andcomprises that portion of the distribution which is equal to and greaterthan four (4) times the peak molecular weight, Mp.

The meaning and significance in the field of polymers of the various GPCmolecular weight distribution parameters as well as solution and neatpolymer viscosities and structural parameters is described in "Scienceand Technology of Rubber," edited by F. R. Eirich (Academic Press,1978); Chapter 3, "Structure Characterization in the Science andTechnology of Elastomers," G. Ver Strate (hereinafter, Ver Strate, pagedesignation).

The absolute molecular weights based on GPC analysis are assigned on thebasis of an elution time calibration defined in terms of hydrodynamicvolume or on the basis of light scattering intensity. For these twomethods the following are the appropriate Mark Houwink and scatteringparameters, all in tetrahydrofuran at 30° C.:

a) for butyl, [η]=5.0×10⁻⁴ M⁰.6 dl/g

b) for polystyrene, [η]1.25×10⁻⁴ M⁰.715 dl/g

and for specific refractive index increment,

for butyl, 0.107 ml/g at 633 nm for the light wavelength.

For linear molecules an elution time calibration based on commerciallyavailable polystyrene samples yields the same Mw as from lightscattering.

The Mw from light scattering can be used with Mv to calculate abranching index as defined below. The Mw/Mv from elution time is alsoused in that index. This latter quantity is not significantly affectedby long chain branching.

III. Viscosity

A. Mooney.

A complete description of the test equipment and procedure can be foundin American Society for Testing and Materials Standards, ASTM D1646,"Viscosity and Curing Characteristics of Rubber by the Shearing DiskViscometer." Values reported herein will refer in a shorthand manner tothe disk size (ML=large), sample warm-up and test run time (e.g., 1+8)and test temperature (e.g., 100° C.); ML (1+8) } 100° C.

B. Solution

Specific values of dilute solution viscosity are not directly reportedbut rather the calculated value of molecular weight based on suchviscosity. Tests for butyl and polyisobutylene are performed usingdiisobutylene as the solvent, typically at 20° C. and at a concentrationin the range of 0.5 to 1.0 milligrams per milliliter. Viscosity averagemolecular weight is calculated using the Mark-Houwink equation: specificviscosity=KMv^(a) where K=34.4×10⁻³, and a=0.64 (see Ver Strate, pages93-95) with specific viscosity in deciliters per gram.

IV. Branching

A general discussion of branching can be found in GPC-Yau, Chapter 12.8,pages 399-401 and VerStrate, pages 107-111. Terms that are frequentlyused include:

A. Linear Chain

This is generally taken to mean a linear backbone of the homopolymer orcopolymer with no branches from the backbone. However, a standard, orreference material which may contain a limited number of branches willsometimes be referred to as a linear chain.

B. Random Branches

Includes short and long chain branching (LCB) which will be stated assuch. Although the expression is qualitative in nature, long impliesmolecular weight of the branch which is similar in magnitude to that ofthe linear backbone.

C. Star Branches

Refers to several (typically linear) branches (e.g., 3, 4 or 6)eminating from the same or closely spaced branch point on the backbone.

Representational figures of branched molecules can be found in thereference Yau at page 450.

D. Branching Index

In an effort to quantify long chain branching the term branching indexwill be used. On a theoretical basis, the branching index is a functionof the intrinsic viscosity of the branched to the linear polymer on aconstant basis such as weight average molecular weight. Since for agiven molecular weight, a branched molecule has a smaller radius ofgyration than its linear counterpart, the branching index, g, will beless than 1.0, and the lower the value, the more highly branched thepolymer. For the purposes of this disclosure the branching index isdefined as follows: ##EQU1## (Mv) SOLN=viscosity average molecularweight measured in diisobutylene and calculated using the Mark-Houwinkequation.

(Mw) LALLS=weight average molecular weight as determined using a lowangle laser light scattering detector in a GPC unit.

(Mw/Mv) GPC=indicated molecular weights as determined by GPC usingdifferential refractive index detector.

a=Mark-Houwink parameter 0.64 for polyisobutylene andisobutylene-isoprene copolymers

b=empirically determined parameter=0.7±0.2 for many polymers; it relatesthe ratio of the intrinsic viscosity of branched and linear polymers ofthe same molecular weight to the ratio of their radii of gyration.

For ease of calculation, the exponential power a/b can be treated asequal to 1.

Green strength, viscosity and elastic memory are important propertiesaffecting the processability of polymers and compounds in variousend-use applications, e.g., tire fabrication. Tire innerliner compounds,for example, require low elastic memory. It would be expected that thisproperty would be enhanced by lower viscosity, but it must be balancedagainst the need to maintain acceptable green strength whichdirectionally increases as viscosity increases. Lower viscosity polymersare also preferred for easier mixing and calendering.

As previously discussed, balancing such properties to achieve anacceptable composition is particularly difficult. Halogenated butylrubber, e.g., chlorinated and brominated butyl rubber, has become thematerial of choice for tire innerliner compositions in view of itsoutstanding air permeability characteristics. With significant effort byrubber manufacturers and tire manufacturers, compositions have beendeveloped with processing properties acceptable for the practical,commercial environment. However, it has been a significant objective toobtain improvements in these properties, and, in particular,improvements which are not dependent on additional additives ordifficult-to maintain process conditions. This has been a particularlydifficult objective to achieve with compositions containing highpercentages of halogenated butyl rubber (for example, up to an including100 percent of the rubber component), which compositions demonstrate thebest air holding characteristics.

One means for achieving the improved properties disclosed herein is byblending polymers or polymer fractions of widely differing and definedmolecular weights to produce "tailor-made" molecular weightdistributions. This results in polymers and polymer compositions withthe unique combination of green strength levels attributable to highermolecular weight butyl polymers combined with lower viscosity and lowerelastic memory (faster stress relaxation) attributable to lowermolecular weight butyl polymers.

The effect of blending can be achieved in a direct synthesis process byutilizing the product produced by two or more polymerization reactorsoperating in parallel or series or two or more polymerization zones in asingle vessel wherein the resulting polymers are mixed. In this manner,each zone or each reactor produces a polymer with molecular weight andmolecular weight distribution characteristics emphasizing specificregion(s) of the molecular weight distribution of the desired finalproduct. Combining the output of the zones or reactors, the blendedproduct incorporates the essential features defined herein.

When blending or direct synthesis means as described are used to achievethe improved properties, the resulting polymer will have a molecularweight distribution such that Mz/Mw is equal to or exceeds 2.0,preferably is equal to 2.0 to about 11.0, more preferably about 2.5 toabout 10.0, most preferably about 3.5 to about 9.0. Where blending meansare used it is convenient to refer to three polymer components forachieving the desired molecular weight distribution of the blendedcomposition, namely a high molecular weight component, a low molecularweight component and a moderate molecular weight component wherein thesum of the three equals 100 percent. Naturally fewer or greater numbersof components differing in molecular weight can be used to achieve thesame end, but three represent a practical compromise. In order toachieve the desired end result, useful polymer blend components are:

    ______________________________________                                        Molecular                                                                     Weight   Mv ×              Crosslinking                                 Component                                                                              10-5        Mw/Mn       Functionality*                               ______________________________________                                        (A) High  15-30  (18-27)                                                                           1.5-3.0 (1.8-2.7)                                                                          .1-.3  (.2)                                 (B) Low  1.5-2.5 (1.8-2.2)                                                                         3.0-6.0 (3.5-5.0)                                                                         1.2-2.2 (1.4-2.0)                            (C) Moderate                                                                           3.0-4.0 (3.3-3.7)                                                                         2.5-5.0 (3.0-4.0)                                                                          .6-.9  (.8)                                 ______________________________________                                         *For 90% network perfection.                                             

The values in parentheses are considered preferable to those firstexpressed. The high molecular weight component is blended at aconcentration of about 8 to about 25 weight percent, preferably about 10to about 20, most preferably about 12 to about 18, for example about 14to about 16; the low molecular weight component at about 0 to about 20weight percent, preferably about 0 to about 15, most preferably about 1to about 12, for example about 2 to about 10; the moderate molecularweight component is employed at a concentration such that the sum of thecomponents equals 100 percent.

Functionality (e.g., halogen and/or unsaturation) of the blend componentis a consideration where strength of the vulcanized or crosslinkedcomposition is a significant factor. Some applications or uses maypermit the use of a polymer blend in which molecular network perfectionis less of an important factor and therefore functionality can be viewedas a secondary consideration. The contribution of functionality of eachcomponent to the crosslinked network will vary depending on themolecular weight of the component to be blended e.g., broadly speaking,less functionality is required for a high molecular weight componentthan for a low in order to incorporate each into a crosslinked network.As will be shown in the examples, even homopolymer polyisobutylene canbe used as a high molecular weight component for blending to achieve thedesired green strength and stress relaxation in the final mixture.

Since the blending approach allows for selection of composition as wellas molecular weight and molecular weight distribution of the blendedcomponents it is appropriate to describe the method by which selectioncan be made where the final blended polymer is to be crosslinked orvulcanized (cured) in a composition for end use application, cureresponse is an important consideration. The general relationshipreferred to above is quantitatively defined by equations presented in apaper by F. P. Baldwin, et al. entitled "Elastomeric Prepolymers forAdhesives and Sealants Provide Improved Strength and Versatility"(Adhesives Age, Feb. 1967), incorporated herein by reference: ##EQU2##where f=functionality of the polymer, mole percent,

m=average molecular weight of the monomer units making up the chainbased on their mole fractions in the polymer (for a copolymer such asbutyl rubber, substantially polyisobutylene, it is approximately 56),

Sa=degree of network perfection, i.e., the fraction of network chainswhich are bounded at each end by a crosslink and hence will contributeto the support of stress.

The equation is an idealized representation since it assumes completeutilization of functionality to crosslinks. By way of example, if a lowmolecular weight, e.g., Mn=65,500, isobutylene-isoprene copolymer isused, the amount of unsaturation required to achieve 90% networkperfection is 1.5 mole percent, whereas a 95% network requires 4.3 molepercent. In contrast a copolymer approximately twice the molecularweight, Mn=127,000 requires unsaturation levels of 0.8 and 1.7 molepercent, respectively. Using a copolymer of significantly highermolecular weight, Mn=503,000, reduces the necessary unsaturation stillfurther, 0.2 and 0.4 mole percent, respectively. Using this approach,the amount of functionality can be readily ascertained and the valuesexemplified herein can be used as guidelines.

The presence of branching in compositions prepared by blending ofcomponents depends on branching present in the component itself. Withregard to branching, more is disclosed below.

The polymers of the present invention, hereinafter collectively referredto for the sake of convenience as butyl rubber, can also be produceddirectly during polymerization, e.g., in a single continuous stirredtank reactor. Generally, such polymers will have highly branchedstructures by incorporating, during polymerization, crosslinking orcationically active comonomers or agents. These agents are referred toas branching agents and preferably are, or contain, structural featureswhich are soluble in the polymerization diluent. More preferably, suchbranching agents are used in conjunction with, or are themselves,stabilizers for the polymer slurry when such a slurry results, e.g.,butyl rubber in methyl chloride (see U.S. Pat. Nos. 4,242,710, 4,358,560and 4,474,924 described earlier). However, the slurry stabilizersdescribed in these patents were recognized as either being chemicallyinert with respect to the cationic polymerization process (e.g.,substantially fully extractable from the polymer after polymerization)or chemically bonded to the polymer (see '924, column 4, lines 43-column5, line 7). The disclosure of bonding was limited to the concept offorming an in situ stabilizer with the preformed copolymer stabilizeracting as a functional lyophile and the product polymer a lyophobe. Theprior art was unaware of the concept of using specific types andconcentrations of additives as branching agents to control molecularweight distribution in order to effect particularly desirable propertiesin the product polymer. The present invention discloses a new controlvariable for producing such preferred polymeric products.

The introduction of branching, preferably long chain branching, resultsin a modification of the molecular weight distribution, and molecularchain configuration, as referred to earlier. Such changes, if controlledin the manner taught, result in advantageous properties and provide ameans for achieving these properties. Since branching is introducedselectively and in a controlled manner, the lower molecular weightpolymer species are substantially branch free, i.e., those species withmolecular weights less than the peak molecular weight, Mp. Based on thebranching index equation previously defined, substantially branch freemeans a distribution or a portion thereof which would have a branchingindex value, g, of greater than 0.9. The disclosure hereinbelow and theexamples demonstrate the manner in which such polymerization selectivityis achieved.

The nature of the polymerization diluent can have important effects onthe polymer produced. Similarly important is the solubility of thebranching agent under polymerization conditions throughout the entirecourse of the polymerization. As butyl is normally produced by slurrypolymerization in methyl chloride diluent, the polymer precipitates outof solution as it is formed. Consequently, when a branching agent isincorporated, it is removed from solution and may become buried withinthe polymer particle so that the additional sites are no longeravailable in the solution phase for subsequent reaction. The actualbranching reactions may be forced to occur within the precipitated butylpolymer in a very different and much more poorly controlled way than hadthe branching agent remained in solution. Gel formation is much morelikely when the reactions occur within the precipitated polymer thanwhen they occur more homogeneously in the solution phase. Furthermore,the amount and nature of the gel produced is highly dependent upon thecatalyst quenching conditions and control is rendered very difficult.Solution polymerization of butyl rubber in diluents such as aliphatichydrocarbons like pentane, hexane, or heptane is advantageous from acontrol viewpoint, when it is desired to produce highly branchedpolymers. Optimum control of the branching reactions is achieved whenthey are totally effected homogeneously in solution and then allcatalyst and active species are killed by quenching prior toprecipitation of the polymer. As noted above, this can be accomplishedby polymerizing butyl rubber in a suitable inert diluent which is a goodsolvent for the polymer and the branching agent. However, branchedstructures, which significantly modify the molecular weight distributioncan also be achieved through the inclusion of reactor-diluent-solublemoieties containing multiple, cationically reactive sites, particularlyin conjunction with slurry stabilizers (as previously discussed toprevent reactor fouling with insoluble gel).

Slurry stabilizers stabilize butyl dispersions produced duringpolymerization in a diluent such as methyl chloride, and prevent themass agglomeration of slurry particles. Hence, slurry stabilizers makeit possible to produce dispersed butyl particles containing gel in thereactor without depositing fouling rubber containing gel on the heattransfer surfaces. Through the use of slurry stabilizers it is possibleto produce a modified butyl rubber containing as much branching and/orgel as is desired in a practical manner without interfering with theability to wash the reactor in order to prepare it for reuse.

Furthermore, through appropriate choice of the branching agent and theamount used, it is possible to exert considerable control over thebranching process so that the desired changes in molecular weightdistribution are achieved. Since crosslinking agents tend to introducerandom long chain branching they modify the entire molecular weightdistribution of the polymer. On the other hand, soluble moietiescontaining multiple reactive sites can be used to introduce a controlledamount of a high molecular weight branched fraction into thedistribution without modifying the entire molecular weight distributionof the polymer. A small amount of a very highly functional and reactivesoluble moiety can be used to introduce a small amount of very highmolecular weight highly branched material into the distribution.Conversely, a larger amount of a less reactive, lower functionalitymoiety can be used to introduce more of the branched fraction, but oflower molecular weight.

The cationically reactive branching agents for use in producing thepolymers of this invention are present during polymerization in anamount effective for producing the desired changes in molecular weightdistribution. Such amounts vary depending on the number and reactivityof the cationically active species, including such variables asmolecular weight and reactivity of the agent (particularly that portionof the agent containing the cationically active moiety). Additionally,polymerization conditions influence the effective concentration, e.g.,batch versus continuous, temperature, monomer conversion, etc. Generallysuch agents are present in an amount, based on the monomers, greaterthan about 0.3 weight percent e.g., about 0.3 to about 3.0 weightpercent, preferably greater than about 0.35 weight percent e.g., about0.35 to about 2.8 weight percent, more preferably greater than about 0.4weight percent e.g., about 0.4 to about 2.7 weight percent, mostpreferably greater than about 0.45 weight percent e.g., about 0.45 toabout 2.6 weight percent, for example greater than about 0.5 weightpercent e.g., about 0.5 to about 2.5 weight percent. Reagents which arenot excessively reactive can be used in a commercial process at, e.g.,about 1.1 to about 2.0 weight percent. The upper limit of concentrationis limited to that concentration which causes the final polymer productto be gelled to an extent which is unacceptable for the intended use ofthe product.

A particularly desirable method of introducing the desired highmolecular weight ends branching is to combine the functions of theslurry stabilizer and the branching agent in one species by use of aslurry stabilizer with multiple active sites in an anchor group. Thelyophilic portion of the slurry stabilizer solubilizes the anchor group,which contains multiple active sites to produce the desired branchedfraction during polymerization, and the lyophilic portion then forms theprotective shield around the butyl slurry particles to provide stericslurry stabilization. Block copolymers of polystyrene and polybutadieneor polystyrene and polyisoprene are examples of molecules which combinethe functions of slurry stabilization and branching agent when butylrubbers are polymerized in methyl chloride diluent as in commercialbutyl rubber processes. The crosslinking comonomer and/or speciescontaining multiple reactive sites is preferentially soluble underpolymerization conditions because then it is more effectively utilizedand the branching reactions can be better controlled. Since thecrosslinking comonomers are typically low molecular weight liquids, theyare soluble in the polymerization diluent of interest, but speciescontaining multiple reactive sites are normally polydienes with limitedsolubility in the normal butyl polymerization diluent (e.g., methylchloride) under reaction conditions. The solubility requirement oftenlimits the molecular weight of polydiene which can be used unless italso contains groups which enhance methyl chloride solubility. Thechoice of these solubilizing groups is restricted by the considerationthat they must not poison the polymerization catalyst used or interferewith the polymerization. As noted above, it is particularly desirablethat the solubilizing group be a lyophilic polymeric chain that can actas a slurry stabilizer so that it serves dual functions. The use ofsolubilizing groups makes it possible to utilize higher molecular weightpolydienes during slurry polymerization of butyl rubbers in methylchloride diluent and, hence, makes possible the production of a morehighly branched, high molecular weight mode during polymerization. Thepolymerization diluent can also be changed to one in which the polydieneis more soluble but such a major process change is less desirable fromeconomic and process viewpoints.

The ability to vary the reactivity of the unsaturated groups as well astheir number per chain affords considerable flexibility in producing abutyl rubber with the desired modification in molecular weightdistribution. For example: the Type IV unsaturation in a1,4-polyisoprene chain is very active under butyl polymerizationconditions and becomes extensively involved in branching reactionswhereas the Type II unsaturation in a 1,4-polybutadiene is very muchless active and, hence, becomes much less extensively utilized inbranching reactions under any given set of conditions. Therefore, a verylow molecular weight polyisoprene (e.g., 500-2500 molecular weight)which is still soluble in methyl chloride can be used to introduce ahighly branched fraction during butyl polymerization. The same number ofbranches can be achieved by using a much higher molecular weightpolybutadiene containing far more unsaturation per chain, but thepolybutadiene would need to be solubilized in the methyl chloride (e.g.,by being present in a block copolymer with a solubilizing agent such aspolystyrene) and would produce a different polymer with a lowerbranching density in the high molecular weight fraction or mode.

Characterization of olefinic residues as Type II, Type IV, etc. is basedon the Boord Classification described by Schmidt and Boord in J.A.C.S.54,751 (1932) and also disclosed in U.S. Pat. No. 4,245,060 (column 3,lines 1-30), both incorporated herein by reference.

Not intending to be bound by theory, it is believed that the mechanismby which the crosslinking comonomers and soluble moieties containingmultiple reactive sites function to produce branching is similar and maybe described as a "graft onto" or "grow-through" mechanism. A growingbutyl chain attacks one of the reactive sites on the comonomer orsoluble moiety containing multiple reactive sites to become attached toit (and can propagate through it) leaving the remaining unsaturatedsites available for similar attack to produce a branched butyl polymerwith two or more butyl chains attached to the same moiety. With acrosslinking comonomer, only two butyl chains can become attached and sorandom long chain branching results and gel is produced whenever thecritical branching value of two per chain is reached. However, when amoiety containing multiple reactive sites is used, the number of butylchains attached to that moiety can be as many as desired since suchchains do not contain active branching functionality and tend toterminate after attachment. It is controlled by setting the number andreactivity of the reactive sites and the amount of branched butylproduced can be controlled by the amount of reactive moiety added to thepolymerization. A high molecular weight ends mode, with many butylchains attached to the reactive moiety, is produced with the remainderof the butyl distribution being unaffected. The molecular weight amountand density in the high molecular weight ends mode are all subject tosome degree of independent control. Judicious use of a soluble moietycontaining multiple reactive sites is a more flexible and controllableway of achieving the desired change in molecular weight distributionthan is use of a crosslinking comonomer.

It is preferred to use soluble moieties containing multiple reactivesites as the branching agent because their use makes it possible toconduct the branching reactions much more nearly in the solution phaseeven when methyl chloride is used as the diluent. This is so because thesolubilizing groups used with the polydiene tend to keep it in solutionor at least at the surface of the precipitated butyl particle even aftera butyl chain has become attached to it. This is especially so when thesolubilizing group is a lyophilic polymer chain so that the polymericbranching agent is a slurry stabilizer and becomes attached to the butylparticle surface to keep the remaining unreacted sites relativelyavailable for branching reactions. Nevertheless, in slurrypolymerization processes, dormant species and catalyst are trappedwithin the precipitated butyl rubber slurry particle where they canproduce additional poorly controlled branching reactions and/or gelformation as the particles warm on leaving the reactor. Thus it isespecially important when branching agents are used in a slurrypolymerization process to efficiently and rapidly quench the slurry tokill all the catalyst and active species before the slurry is allowed towarm.

As disclosed herein, it is possible to go one step further and toconduct the polymerization process as a solution polymerization.Solution polymerization also permits the direct use of polydienes andpartially hydrogenated polydienes as the branching moiety without theneed for other solubilizing groups on the polydiene. Thus polybutadiene,polyisoprene, polypiperylene, natural rubber, and styrene/butadienerubber can all be employed as the branching moiety during solutionpolymerization of butyl rubbers in a solvent such as hexane.

The reactive site or functional group on the functional lyophileparticipates in the polymerization as discussed above and becomes thesite at which the butyl chain becomes attached to form the block orgraft copolymer. If the functional lyophile contains more than onefunctional group, then a butyl chain can become attached at eachfunctional group and a number of butyl chains become attached to thelyophile. The multifunctional lyophile then becomes a means of linkingmany butyl chains together (by virtue of their attachment to the samelyophile molecule). The number of butyl chains which are linkedtogether, and thus the molecular weight of the linked moiety, is easilycontrolled by controlling the functionality of the multifunctionallyophile. Hence, a high molecular weight end mode of any desiredmolecular weight is readily prepared in situ during polymerization. Thearchitecture of the linked moiety can also be controlled by the spacingof the functional groups on the multifunctional lyophile. Thus a clusterof butyl chains can be attached at intervals along the lyophile chain.In addition, the amount of the multifunctional lyophile added to thepolymerization controls the amount of the high ends fraction formed.This is a convenient method to control the amount, nature and molecularweight of the high ends mode.

Generally, modification of the molecular weight distribution is achievedby incorporating during polymerization of the polymers an effectiveamount of functional reagent selected from the group consisting ofpolymers and copolymers comprising functional groups capable ofcopolymerizing or forming a chemical bond with the product polymer, thefunctional group comprising cationically active halogen or cationicallyactive unsaturation and such polymers and copolymers preferablycomprising lyophilic polymerization diluent soluble moiety. Thecationically active unsaturation comprises a polydiene and partiallyhydrogenated polydiene selected from the group consisting ofpolybutadiene, polyiosprene, polypiperylene, natural rubber,styrene-butadiene rubber, ethylene-propylene diene monomer rubber,styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers.

Classes of functional polymeric reagents which are useful arerepresented by the following formulae: ##STR1## wherein R₁, R₂ and R₃=hydrogen or alkyl group

R₄, R₅ =alkyl group

x=halogen, e.g., chlorine or bromine

n=4-100

alkyl group having 1 to 15 carbon atoms, preferably 1 to 4; non-limitingexamples include methyl and ethyl.

Suitable reagents in this class include chlorinated butyl and brominatedbutyl. ##STR2## wherein R₁ =alkyl (e.g., as in (1), above) or aryl

R₂, R₃ =alkyl

x=halogen, e.g., chlorine or bromine

n=4-100

aryl group, including phenyl and tolyl.

Suitable reagents in this class include hydro-chlorinated polyisoprene,hydrobrominated polyisoprene, isobutylene-vinylbenzyl chloride copolymerand chlorinated polystyrene. ##STR3## wherein R₁, R₂ =hydrogen, alkyl(as in (1) or (2) above), aryl (as in (2) above) or alkenyl

R₃, R₄ =alkyl

n=7-1,000

alkenyl group including ethene and propene.

Suitable reagents in this class include polybutadiene, polyisoprene andpolypiperylene.

As discussed previously with regard to the blending of polymers,molecular weight and molecular weight distribution criteria are criticalfor obtaining the desired polymer products and achieving the uniquebalance of properties, i.e., green strength and stress relaxation. Theamount of branching agent fed to the reactor and polymerizationconditions, e.g., conversion, should be controlled in order to obtainuseful polymers, i.e., those with high ends fraction of from about 8 toabout 25 weight percent; preferably about 10 to about 20, mostpreferably about 12 to about 18, for example about 14 to about 16 weightpercent. As described previously, for the purposes of this invention,the amount of high ends fraction in useful polymers comprises thatportion of the molecular weight distribution which is equal to orgreater than 4 Mp, preferably about 5 Mp, most preferably about 6 Mp,for example about 8 Mp. Useful polymers are obtained when the peakmolecular weight of the polymer, Mp, is greater than about 250,000; itis preferable that Mp is about 250,000 to about 850,000; more preferablyabout 270,000 to about 800,000; most preferably about 290,000 to about750,000; for example about 300,000 to about 700,000.

Compositions can also be prepared by utilizing the principles of theblend approach, described hereinbefore, in combination with directlypolymerized branched polymers. Useful compositions are prepared byblending highly branched polymers with polymers that are essentiallylinear. The resulting composition has the desirable green strength andstress relaxation characteristics when the blended composition has thedefined molecular weight criteria.

Many properties of a rubber (such as extrusion rate, die swell, mixingtime, filler dispersion, cold flow, green strength, tire cordstike-through, building tack, adhesion, the various vulcanizateproperties, etc.) are strongly influenced by its molecular weightdistribution and branching. Different balances between these variousproperties can be achieved by varying the molecular weight, molecularweight distribution and branching. Thus, the techniques of thisinvention for introducing controlled amounts and types of branching intobutyl rubbers and for modifying their molecular weight distributions ina controllable manner enables production of specialized grades of butylrubber which are especially suitable for particular applications. Thesetechniques make it possible to achieve a better compromise between thevarious and often conflicting properties desired in a rubber formulationduring processing, fabrication and end use in a particular application.Particularly advantageous properties are obtained from halogenated butylrubber prepared using the butyl polymers described herein for subsequenthalogenation. The halogenated polymers, e.g., brominated butyl andchlorinated butyl can be used to produce tire innerliner compositionswith improved processing properties such as higher green strength, andfaster stress relaxation compared to similar halogenated butylcompositions absent the modified structure and molecular weightdistribution.

The polymers of this invention, wherein green strength and stressrelaxation rate have been increased, are particularly useful incompositions for products produced by extrusion, calendering, andinjection, transfer and compression molding. Such products include tirecomponents such as sidewalls, sidewall veneers, carcasses and treads,innertubes, wire and cable, hose, sheeting, film, automotive andmechanical goods, sponge products, pharmaceuticals, adhesives, sealants,etc. The polymers are also particularly useful in blends comprisingother elastomers and plastics, including cured compositions as well asthermoplastic and dynamically vulcanized blends. One skilled in the artwill recognize that such compositions can typically include additionalcomponents such as reinforcing and nonreinforcing fillers, extenders andplasticizers, process aids, antioxidants and antiozonants, colorants,etc.

The invention is further illustrated by the following examples which arenot to be considered as limiting its scope.

EXAMPLE 1

Polymer compositions were prepared by blending polymers differing inmolecular weight. The compositions were blended in solutions of 10% byweight polymer in hexane, then steam stripped and dried on a rubbermill. The resulting polymer blends were then tested according to thetests described earlier. The polymers prepared in these blendingexperiments where characterized using the GPC method without the lowangle laser light scattering (LALLS) detector which was later found toaffect the determination of high molecular weight components (subsequenttests using LALLS indicated a decrease of about 0.4 units for the valueof Mz/Mw as compared to values measured by refractive index).

The blends were prepared using as the high molecular weight component(Mv=2,100,000), polyisobutylene manufactured by Exxon Chemical Co. anddesignated Vistanex® L-140; as the moderate molecular weight component,butyl rubber manufactured by Exxon Chemical Co. and designated Butyl 365(IIR is an accepted generic abbreviation for butyl, isobutylene-isoprenerubber); as the low molecular weight component, low molecular weightbutyl rubber (Mv=220,000), designated as IIR LMW. The other,commercially available polymers, are also manufactured by Exxon ChemicalCo. and are identified as follows: CIIR 1065=Chlorobutyl rubber, grade1065; CIIR 1066=Chlorobutyl rubber, grade 1066; CIIR 1068=Chlorobutylrubber, grade 1068; IIR 268=butyl rubber, grade 268. Test results arereported in Table 1 for blends demonstrating the improved properties ofthe invention (blends A and B).

                  TABLE 1                                                         ______________________________________                                                     4Mp,                                                                          High              Green  Relaxed                                        Mz/   Ends,   Mooney    Strength,                                                                            Stress,                                        Mw    wt. %   Viscosity.sup.(a)                                                                       psi    psi                                     ______________________________________                                        1 IIR 365                                                                              2.2     5.0     44      28.0    6.4                                  2 CIIR 1065                                                                            2.4     4.0     42      27.6    7.9                                  3 Blend A.sup.(b)                                                                      2.8     8.0     45      29.3    8.0                                  4 CIIR 1066                                                                            2.5     4.0     55      29.7   10.3                                  5 Blend B.sup.(c)                                                                      3.0     11.0    49      32.4   10.1                                  6 CIIR 1068                                                                            2.4     4.0     71      31.9   12.8                                  7 IIR 268                                                                              2.1     3.3     69      32.2   12.1                                  ______________________________________                                         .sup.(a) ML 1 + 8 at 100° C.                                           .sup.(b) Composition: 10% Vistanex L140 (M.sub.V = 2.1M), 80% IIR 365         (M.sub.V = 320K), 10% IIR LMW (Mv = 220k).                                    .sup.(c) Composition: 15% Vistanex L140, 85% IIR 365.                    

Comparison of polymers 1 through 4 shows that blend A exhibits the greenstrength of a higher Mooney viscosity rubber like CIIR 1066, atviscosity and stress relaxation levels comparable to lower Mooneyviscosity polymers like CIIR 1065 or IIR 365. Comparing polymers 4-7shows that blend B displays the green strength of CIIR 1068 or IIR 268and the stress-relaxation capability of CIIR 1066, at significantlylower viscosity than these polymers. Stated another way, theexperimental blends with molecular weight distribution features selectedto improve specific performance properties exhibited higher greenstrength and faster stress relaxation compared to typical, commercialpolymers of equivalent Mooney viscosity.

Polymers blends were also evaluated in compositions further comprisingcarbon black, rubber process oil and other ingredients typically used inend use applications, e.g., a tire innerliner formulation. Thecomposition was mixed in a laboratory internal mixer (size B Banbury®)using the following formulation (parts by weight):

    ______________________________________                                        Polymer               100                                                     Carbon Black (type N660,GPF)                                                                        50                                                      Naphthenic Process Oil.sup.(a)                                                                      8                                                       Processing aid.sup.(b)                                                                              7                                                       Stearic acid          2                                                       Magnesium oxide.sup.(c)                                                                             0.15                                                    Zinc oxide            3                                                       MBTS.sup.(d)          1                                                       Sulfur                0.5                                                     ______________________________________                                         .sup.(a) Flexon ® 641 (Exxon Chemical Co.)                                .sup.(b) Struktol ® 40MS (Struktol Co.)                                   .sup.(c) Maglite ® K (Merck)                                              .sup.(d) 2,2Benzothiazyl disulfide                                       

Several additional blends were prepared with different proportions ofhigh molecular weight polyisobutylene (grade Vistanex L-140) and butylrubber (grade Butyl 365) as indicated in footnote (c) of Table 1 above.For comparative purposes, commercially produced samples of halogenatedbutyl differing in Mooney viscosity were also tested. The blends andtest results are summarized in Table 2a and illustrated in FIG. 1.

                  TABLE 2a                                                        ______________________________________                                                Blend.sup.(a) Green    Relaxed                                                            Moderate  Strength,                                                                            Stress,                                  Polymer   High MW   MW        psi.sup.(b)                                                                          psi.sup.(c)                              ______________________________________                                        Blend 1    8        92        30.0    4.7                                     Blend 2   15        85        31.4    5.0                                     Blend 3   25        75        34.4    6.2                                     Blend 4   45        55        39.7    9.4                                     CIIR 1065 (I)                                                                           --        --        29.6    4.6                                     CIIR 1066 (II)                                                                          --        --        32.3    7.0                                     CIIR 1068 (III)                                                                         --        --        33.7    9.1                                     ______________________________________                                         .sup.(a) Blend 2 corresponds to Blend B of Table 1.                           .sup.(b) Peak stress value as shown in FIG. 1.                                .sup.(c) 4 minute stress as shown in FIG. 1.                             

From an examination of the data as shown in FIG. 1, it is immediatelyapparent that the blend properties are significantly different in kindcompared to the commercially produced polymers. The blend compositions,particularly those with sufficient high molecular weight ends, exhibitsignificantly lower 4 minute relaxed stress than standard polymers atequivalent levels of green strength. Testing of the innerlinercompositions for green strength and stress relaxation was accomplishedby using a sample calendered to approximately 0.070 inches thickness andtested as previously described.

The manner in which the molecular weight distribution is modified, e.g.,broadened, can significantly affect properties. Specific compositionalfeatures are necessary for improved properties, and broadening can beexcessive as well as inadequate. Additional polymer blends were preparedas described above in order to achieve altered molecular weightdistributional features, Table 2b. Blend A is the same composition asabove (which had improved properties compared to a higher Mooneyviscosity commercial polymer. In Blend C, the amounts of both high andlow MW components were increased to 20%. This resulted in essentially nochange in Mooney viscosity or green strength, but a 10% increase in therelaxed stress level.

In the second group of samples in Table 2b, Butyl 365 is compared withtwo blend compositions of slightly lower Mooney viscosity. Blends D andE both contain increased amounts of the low MW component with the highMW component held at 20%. This results in lower green strength levelsthan Butyl 365, and slower relaxation (higher relaxed stress levels).

                  TABLE 2b                                                        ______________________________________                                        Properties of Polymer Blend Compositions.sup.(a)                                           4Mp,                                                                          High              Green  Relaxed                                              Ends,   Mooney    Strength,                                                                            Stress,                                 Mz/Mw        wt. %   Viscosity.sup.(a)                                                                       psi    psi                                     ______________________________________                                        Blend A 2.8      8.0     45      29.3   8.0                                   Blend C.sup.(b)                                                                       2.7      11.0    46      29.3   8.8                                   Butyl 365                                                                             2.2      5.0     44      28.0   6.4                                   Blend D.sup.(c)                                                                       2.8      11.0    41      26.8   7.6                                   Blned E.sup.(d)                                                                       3.0      6.0     40      26.0   6.5                                   ______________________________________                                         .sup.(a) ML 1 + 8 at 100° C.                                           .sup.(b) Composition: 20% Vistanex L140, 60% IIR 365, 20% IIR LMW             .sup.(c) Composition: 20% Vistanex L140, 30% IIR 365, 50% IIR LMW             .sup.(d) Composition: 20% polyisobutylene containing a low concentration      of isoprene (Mv = 1.0M), 45% Butyl 365, 35% IIR LMW (Mv = 170k)          

EXAMPLE 2

A series of batch dry box polymerizations were run to show the effect oflow levels of a low molecular weight reactor-diluent-solublepolyisoprene polymer on the molecular weight distribution of butylrubber slurry polymerized in methyl chloride diluent. The low molecularweight soluble polyisoprene used in this series of batch polymerizationswas identified as AI-8803-084-5. It was prepared by "living" anionicpolymerization of highly purified isoprene in cyclohexane diluent usingsecondary butyl lithium catalysis. It was a narrow molecular weightdistribution liquid polymer with a molecular weight of 530 by GPC. Thisliquid polyisoprene was primarily an isoprene heptamer initiated from asecondary butyl group. It was readily soluble in methyl chloride or atypical butyl feed blend and contained about seven reactive double bondsper chain. Each polyisoprene molecule was thus capable of tying sevenbutyl rubber chains together (if all the unsaturated sites wereutilized) to form a bush-type branched fraction consisting of sevenbutyl chains attached to each polyisoprene molecule. The amount of thishigh ends branched fraction is readily controlled by varying the amountof polyisoprene added to the polymerization.

The batch dry box polymerizations were conducted as follows: thepolymerizations were conducted in a 500 ml. 3-neck reaction flask setupin a glove box having an oxygen-free and moisture-free nitrogenatmosphere. The flask was cooled to -95° C. by immersion in a controlledtemperature liquid nitrogen cooled heat transfer bath. It was fittedwith a thermometer, cooled dropping funnel and stirrer. Typically theflask is charged with 460 g. of a feed blend in methyl chloride and thena catalyst solution in methyl chloride is slowly dripped in to initiatepolymerization while stirring of the bath is continued in order tomaintain the desired polymerization temperature. The feed blend istypically defined by a "B" number, e.g., B-3. The B number is ashorthand reference of the approximate weight percent concentration ofisoprene relative to isobutylene, e.g., 3.0 g. isoprene with 97.0 g.isobutylene calculates as 3.09 and is cited as B-3.

After sufficient catalyst solution has been added to make the desiredamount of polymer, the polymerization is quenched by addition of coldmethanol (typically 25 ml.) and then transferred to a vented hood whereit is allowed to warm and flash off the methyl chloride and unreactedmonomers. Additional methanol containing a trace of butylatedhydroxytoluene (BHT) stabilizer is added as the reactor liquids flashoff in order to protect the polymer from degradation prior to recovery.After the monomer is completely flashed off, the polymer is kneaded andwashed in isopropanol to remove catalyst residues and then vacuum ovendried at 80° C. with 0.2 wt. % BHT added as an antioxidant. The driedpolymer is then used for evaluation and characterization. In the controlrun, 1, the reaction was charged with a 10.9 wt.% B-3 feed in methylchloride and chilled to -97° C. before the 0.3 wt. % EADC catalystsolution was dripped in to produce polymer. Catalyst solution wasdripped in slowly over the course of five minutes while stirring andmaintaining temperature between -97° and -93° C. before quenching andrecovering the polymer as usual. In the control run a 53% conversion ofmonomer to polymer was realized and the recovered, dried polymer was atough, rubbery, butyl polymer with a viscosity average molecular weightof 431,000, Mp of 420,000 and INOPO of 9.5 (approx. 1.4 mole %isoprene). GPC analyses showed the polymer to have a typical butylmolecular weight distribution skewed toward the low molecular weightspecies with an Mz/Mw ratio of 1.7 and less than about 0.7% in the highends (calculated, in this and succeeding examples, as the amount ofpolymer present in the molecular weight distribution at molecularweights equal to and greater than 4 Mp).

In companion run 2, the same feed blend was used with 0.5 wt. % onmonomers of the low molecular weight polyisoprene AI-8803-084-5, added.It was readily soluble and dissolved quickly in the feed blend. The 0.3wt. % EADC catalyst solution was dripped in slowly over the course of 17minutes while stirring and maintaining temperature between -97° and -94°C. to produce polymer. After quenching and recovery, 16.50 g. (33%conversion) of a tough, rubbery butyl polymer with an Mv of 308,000 andMp of 270,000 was obtained. The low molecular weight polyisopreneapparently contained some poisons as about twice as much catalyst wasrequired as in the control run to produce polymer and the polymerviscosity average molecular weight was reduced from 431,000 to 308,000.Nevertheless, molecular weight distribution broadening with theproduction of a high molecular weight tail was achieved (estimated to beabout 4%). The polymer had an Mz/Mw ratio of 2.1 by GPC using an RI(refractive index) detector and a higher Mz/Mw ratio of 3.4 using LALLSto better resolve the high molecular weight species. It contained 1.1mole % enchained isoprene with 0.9 wt. % of the low molecular weightpolyisoprene mainly incorporated in the high ends tail. In a secondcompanion run 3, a higher level of the low molecular weight polyisopreneof 1.0 wt. % on monomers was used. In this run, 60 ml. of the catalystsolution was dripped in over the course of 11 minutes at apolymerization temperature between -97° and -95° C. to produce polymer,and 11.17 g. (22% conversion) of a tough, rubbery butyl polymer with anMv of 110,000 and Mp of 80,000 was recovered. This higher level ofpolyisoprene produced even more catalyst and molecular weight poisoning.Nevertheless, even more molecular weight broadening with still more ofthe high molecular weight tail was achieved (estimated to be about 6%).This polymer had an Mz/Mw ratio of 2.7 by GPC using an RI detector and aratio of 4.2 using LALLS. Even at the low conversion achieved in thisrun, it contained 0.8 wt. % of the low molecular weight polyisopreneincorporated mainly in the high ends tail. (The amount of incorporatedpolyisoprene is an estimate based on unsaturation measurements; to theextent unsaturation in the polyisoprene has been lost, the incorporationis even higher.) Clearly the low molecular weight polyisoprene is beingincorporated during polymerization to broaden the molecular weightdistribution by producing a high ends fraction consisting of multiplebutyl chains attached to each polyisoprene molecule. This broadening isachieved without any gel formation even with slurry polymerizationbecause the limited functionality of the low molecular weightpolyisoprene will not permit the attachment of more than seven butylchains to each polyisoprene molecule.

This example shows that a high molecular weight fraction can be producedduring polymerization through the use of a methyl chloride solublepolymer containing multiple cationically reactive unsaturation sites.The amount of the high ends fraction can be controlled by the amount ofthe reactive soluble polymer added; the molecular weight of the highends fraction can be controlled by the amount and reactivity of thefunctionality on the reactive soluble polymer. The molecular weight ofthe high ends fraction can be raised by operating at high conversion toattach more butyl chains to each polyisoprene molecule and/or by raisingthe molecular weight of the polyisoprene so that each molecule containsmore reactive unsaturation (sites). As the molecular weight is raised,the polyisoprene becomes less soluble in methyl chloride and in order tomaintain it in solution it becomes necessary to introduce solubilizinggroups into the polyisoprene (preferentially as a solubilizing block) orto change the diluent to make it a better solvent for polyisoprene. Thelatter change also has the advantage of making the diluent a bettersolvent for butyl and changes the nature of the slurry and in the limitresults in a change from slurry polymerization to solutionpolymerization. Raising the molecular weight and, hence, the number ofdouble bonds per chain of the polyisoprene too much can produce suchextensive branching that gel results. Thus there is a limited range ofmolecular weights over which polyisoprene or polyisoprene containingsolubilizing groups is useful as a functional polymer for introducinghigh ends branching into butyl during polymerization.

Other polydienes (i.e., polybutadiene, SBR rubbers, etc.) are alsouseful for introducing the high ends branched fraction but have adifferent useful molecular weight range depending upon the number andcationic reactivity of the double bonds. The Type IV double bonds inpolyisoprene are very reactive under butyl polymerization conditions andso very low molecular weight soluble polyisoprenes are useful forintroducing branching as shown in this example. The Type II double bondsin 1,4-polybutadiene are much less reactive and so a much highermolecular weight polymer are required to produce the same degree ofbranching in the butyl. With these less reactive polydienes,solubilizing groups are required to make the high molecular weightpolymers soluble in the polymerization diluent, e.g., methyl chloride,for use during slurry polymerization of butyl rubbers as is normallypracticed. Suitable lyophilic groups have a Flory-Huggins interactionparameter with the polymerization diluent of less than 0.5. Suchmaterials include polystyrene, polyvinyl chloride, polyvinyl bromide,neoprene, mono-, di- and trisubstituted styrenes (the substituents beinghalogen, such as chlorine, or lower C₁ -C₅ alkyl groups, as illustratedby alpha-methyl styrene, para-t-butyl styrene, p-chlorostyrene andsimilar ring chlorinated styrenes).

EXAMPLE 3

A series of batch dry box runs similar to those described in theprevious example was run to evaluate a styrene/butadiene block copolymeridentified as KR03-K-Resin® (Phillips Chemical Company) as a branchingagent during butyl polymerization. KR03-K-Resin is a block copolymer(containing 62 mole % styrene and 38 mole % butadiene) with a viscosityaverage molecular weight of 145,000 by toluene solution viscosity.(Mn=98,500, Mw=213,100 by GPC). It is a diblock polymer coupled from thepolybutadiene so that the polybutadiene is in the central portion of theblock copolymer. The polybutadiene microstructure, which is important indetermining cationic activity during butyl polymerization, is about 12%1,2 addition and 88% 1,4 addition with mixed cis/trans configuration,but mostly cis. The dry box runs were made using a 10.9% B-3 feed using48.5 g. isobutylene and 1.5 g. isoprene in each run. All polymerizationswere run with the cooling bath temperature set at about -66° C. andpolymerizations were initiated by dripping in a 0.18% solution of AlCl₃in methyl chloride as catalyst.

In the control run with no branching agent added, Run 1, 13 ml. ofcatalyst solution was dripped in over the course of three minutes and43.47 g. (87% conversion) of a tough, white, rubbery butyl rubber wasrecovered. The polymer had an Mv (dilute solution viscosity, DSV) of245,700, an Mp of 230,000 and INOPO of 8.5 with a typical butylmolecular weight distribution. The Mz/Mw ratio by GPC was 1.5 and it isestimated that less than 0.7% was present in the high ends.

In run 2, 0.5 g. of KR03-K-Resin (1% on monomers) was dissolved in thefeed blend prior to initiating polymerization. In this run, 17 ml. ofthe catalyst solution was dripped in over the course of eleven minuteswhile stirring and maintaining temperature in the reactor between -64°and -53° C. and 44.03 g. (87% conversion) of a tough, white, rubberybutyl rubber with a branched fraction attached to the KR03-K-Resin wasrecovered. This polymer had an Mv (DSV) of 274,400, an Mp of 240,000with an INOPO of 9.0. This polymer had a branched high ends fraction ofabout 4.5% and an Mz/Mw ratio of 2.5 by GPC.

In run 3, 1.0 g. of KR03-K-Resin (2% on monomers) was dissolved in thefeed prior to initiating polymerization. In this run, 18 ml. of thecatalyst solution was dripped in over the course of ten minutes and46.03 g. (90% conversion) of a tough, white, rubbery butyl rubber with abranched fraction attached to the KR03-KResin was recovered. Thispolymer had an Mv (DSV) of 298,300, an Mp of 250,000 and INOPO of 9.3.It had an Mz/Mw ratio of about 9 by GPC/LALLS with about 20% in the highends.

These results show that KR03-K-Resin, a styrene-butadiene blockcopolymer, can be an effective agent to introduce controlled high endsbranching into butyl rubber during polymerization if it is used at anappropriate concentration. An additional benefit of the KR03-K-Resinpreviously disclosed in U.S. Pat. No. 4,474,924 is that it acts as aslurry stabilizer to improve reactor operation. The slurry produced inthe control run 1 agglomerated completely as made whereas stable, milky,slurries were produced in runs 2 and 3 with KR03-K-Resin added to thefeed. Furthermore, under the conditions used, there was no gel in thefinished polymers produced in the runs with KR03-K-Resin. Under thesebatch polymerization conditions, KR03-K-Resin is a desirable materialfor introducing a controlled high ends fraction into butyl rubber duringpolymerization.

EXAMPLE 4

A series of batch dry box runs similar to those of Example 3 was runusing KROl-K-Resin® as the branching instead of KR03-K-Resin.KROl-K-Resin is a styrene/butadiene block copolymer (Phillips ChemicalCompany) similar to KR03 but made with a different coupling agent and ithas a different molecular weight. Its composition is 62 mole % styreneand 38 mole % butadiene with a viscosity average molecular weight of140,000 by toluene solution viscosity (Mn=103,500, Mw=165,700 by GPC).Like KR03, the polybutadiene is attached to the coupling agent so thatit comprises the central core of the block copolymer and thepolybutadiene microstructure is similar to that of KR03. The runs wereall made using a 10.9% feed containing 48.5 g. isobutylene and 1.5 g.isoprene in each batch reactor along with the desired amount ofKROl-K-Resin where used. The cooling bath temperature was -66° C. and an0.18% solution of AlCl₃ in methyl chloride was used as the catalyst.

The control run with no branching agent was run 1 as already describedin Example 3. In run 1 of this example, 0.5 g. of KROl-K-Resin (1% onmonomers) was dissolved in the feed blend prior to initiatingpolymerization and 20 ml. of the catalyst solution was dripped in overthe course of fourteen minutes while stirring and maintainingtemperature between -63° and -55° C. in the reactor. In this run, 37.97g. (76% conversion) of a tough, white, rubbery butyl rubber containing abranched high ends fraction attached to some of the KROl-K-Resin wasrecovered. This polymer had an Mv (DSV) of 257,100, Mp of 230,000 andINOPO of 8.7. It had an Mz/Mw ratio of 3.4 by GPC/LALLS and alsoproduced about 8.5% high ends branching of the molecular weightdistribution.

In run 2, 1 g. of the KROl-K-Resin (2% on monomers) was dissolved in thefeed and 22 ml. of the catalyst solution was dripped in over the courseof eight minutes while stirring and maintaining reactor temperaturebetween -63° to -53° C. to produce 37.65 g. (75% conversion) of a tough,white, rubbery butyl rubber containing a branched high ends fractionattached to some of the KROl. This polymer had an Mv (DSV) of 251,700,Mp of 220,000 and an INOPO of 8.8. It had an Mz/Mw ratio of 3.9 byGPC/LALLS and about 15.5% of a high molecular weight fraction in thedistribution. Adjustment of polymerization conditions can increase Mpand raise it to the preferred level of greater than about 250,000.

No gel was found in any of these polymers and like KR03, KROl acted as aslurry stabilizer to yield stable milky slurries in runs 1 and 2 ascompared to the completely agglomerated mass of rubber produced in thecontrol run. Thus KROl can also be a useful material for introducing acontrolled high ends fraction into butyl during polymerization.

In order to show the importance of the unsaturation in the polybutadienefor producing this high ends branched fraction, run 3 was made in whichthe KROl resin was partially hydrogenated to eliminate most of theactive unsaturation prior to its use as a branching agent in a butylbatch dry box polymerization. This resin identified as 85% HKROl wasprepared by the use of diisobutyl aluminum hydride as a chemicalreducing agent to hydrogenate and remove most of the active unsaturationin the polybutadiene portion of the KROl-K-Resin without affecting thepolystyrene blocks. The hydrogenation was effected by dissolving theKROl in dry toluene to give a 10% solution; adding the diisobutylaluminum hydride at 1 mole per mole of butadiene and then heating to 90°C. for two hours before quenching, washing and recovering the particallyhydrogenated KROl resin. The recovered 85% HKROl was essentiallyunchanged from the starting KROl in molecular weight, but 85% of thepolybutadiene unsaturation had been hydrogenated and removed. Theremaining unsaturation was predominantly the more inert trans in-chaintype. In the run with this partially hydrogenated KROl, 0.5 g. of the85% HKROl (1% on monomers) was dissolved in the feed blend and 12 ml. ofthe catalyst solution was dripped in over the course of ten minutes toproduct 31.32 g. (62% conversion) of a tough, white, rubbery butylrubber. It has an Mv(DSV) of 225,200, Mp of 215,000 and an INOPO of 8.5with a typical butyl molecular weight distribution. The Mz/Mw ratio byGPC was 1.6 with less than about 0.7% in the high ends. The viscosityaverage molecular weight was slightly lower than the control molecularweight of 245,700 and there was no evidence of any high ends branchedfraction. The slightly reduced molecular weight probably reflects thepresence of some unreacted 85% HKROl resin in the polymer, but may alsobe due to slight molecular weight depression caused by the 85% HKROl inthe reactor. These results show that removing the active unsaturation inthe KROl resin by hydrogenation has rendered it effectively inert duringbutyl polymerization and prevented it from acting as a branching agentto produce a controlled high ends branched fraction in butyl rubberduring polymerization. A lower level of hydrogenation can be used toreduce the cationic activity of the polybutadiene and achieve thedesired level of residual activity to produce the desired degree of highends branching.

In order to show the generality of partial hydrogenation for reducingeffective cationic activity, a partially hydrogenated KR03 resin samplewas prepared and evaluated as a branching agent in a batch dry box butylpolymerization. The KR03 resin was hydrogenated as just described forthe KROl resin and again an 85% reduction in the polybutadieneunsaturation was achieved without affecting the polystyrene blocks ofthe KR03 resin or its molecular weight. This 85% HKR03 resin, identifiedas 7887-37, was added in run 4 at 0.5 g. (1% on monomers) to a B-3 batchpolymerization. In the run with the partially hydrogenated resin, 12 ml.of catalyst solution was dripped in over the course of eleven minutes toproduce 31.31 g. (62% conversion) of a tough, white, rubbery butylrubber with an Mv (DSV) of 250,200, Mp of 230,000 and an INOPO of 8.5with a typical butyl molecular weight distribution. The Mz/Mw ratio byGPC was 1.7 with less than about 1% high ends. The molecular weight wasonly slightly higher than the control and there was no evidence of ahigh ends branched fraction. Removing most of the active unsaturation inthe KR03 resin by partial hydrogenation made it quite inert during butylpolymerization and prevented it from introducing a high ends branchedfraction into the polymer when added to a butyl polymerization.

The partially hydrogenated K-Resins used in these experiments were veryeffective slurry stabilizers and produced finer and more stable milkydispersion of the butyl rubber in methyl chloride than even theunhydrogenated K-Resins, but they were not significantly incorporatedinto the polymer during polymerization to produce a branched high endsfraction as were the unhydrogenated K-Resins. The hydrogenated K-Resinswere absorbed on the butyl slurry particles and enhanced slurrystability whereas the unhydrogenated K-Resins became chemically attachedto the butyl polymer during polymerization and produced a branched highends fraction. The GPC test and Mz/Mw ratios already cited are evidenceof this difference. Extraction experiments provide further proof of thisdifference. The extraction experiments were performed by recovering thebutyl rubber from the batch experiment in methyl/ethyl ketone which is anon-solvent for butyl but a solvent for K-Resins or hydrogenatedK-Resins. Two MEK extractions are preformed and the extracts combined torecover the MEK soluble resin and the MEK insoluble rubber separately.In runs with the hydrogenated resins, nearly all of the K-Resins can beextracted and recovered in unchanged form. With the unhydrogenatedK-Resins, very little of the resin can be extracted, and the extractedmaterial has butyl attached to it. These extraction experiments providefurther proof that the unsaturation in the polybutadiene portion of theK-Resins is active during butyl polymerization so that butyl chainsbecome attached to it to produce a high ends branched fraction.Hydrogenation of the unsaturation reduces this reactivity and reducesthe effectiveness of the K-Resins as branching agents.

EXAMPLE 5

A series of butyl polymerization runs were made in a butyl continuouspolymerization reactor with various amounts and types of K-Resins. Thereactor permitted polymerization experiments to be run under continuouspolymerization conditions which closely simulated commercialpolymerization conditions. The rector was a modified, baffled, drafttube containing well stirred tank type reactor of nominal one-galloncapacity and containing 2.86 square feet of heat transfer surface toremove the heat of polymerization and maintain the rector contents atpolymerization temperature. Separate feed and catalyst streams could bechilled and metered continuously into the reactor and the effluentcontinuously overflowed through a 3/4-inch overflow line into chilledproduct slurry receivers for quenching and recovery. Reactor temperaturewas maintained and controlled by circulating a heat transfer fluid at acontrolled rate and temperature through channels within the reactor heattransfer surfaces.

The equipment is designed to meter and chill four separate streams intothe reactor to establish a steady-state set of polymerizationconditions. Normally a monomer feed, an additive solution (i.e., K-Resinsolution), a diluent stream, and a catalyst solution were fed into thereactor to establish the steady state. In a control polymerization withno K-Resin, run 1, a steady state was achieved with the following feedsinto the reactor, all in grams per minute:

    ______________________________________                                        Isobutylene      50.403                                                       Isoprene         1.375                                                        Methyl Chloride  135.465                                                      AlCl.sub.3       0.047                                                                         187.29                                                       ______________________________________                                    

Reactor temperature was controlled at -96.0° C. and at the steady-state,monomer conversion was 94.5% with production of a 26.1% slurry. Thereactor effluent was rather thick and lumpy and reactor fouling forcedtermination of the run after five hours. The butyl rubber produced atsteady state had an INOPO of 10.7 with an Mv=528,500 and Mp=500,000. Ithad a typical butyl molecular weight distribution with an Mz/Mw ratio byGPC of 1.6 with less than 0.7% high ends.

In another control polymerization with no K-Resin, run 2, a steady statewas achieved with the following feeds into the reaction, again, all ingrams per minute:

    ______________________________________                                        Isobutylene      53.590                                                       Isoprene         1.461                                                        Methyl Chloride  123.388                                                      AlCl.sub.3       0.030                                                                         178.47                                                       ______________________________________                                    

Reactor temperature was controlled at -94.3° C. and at the steady-state,monomer conversion was 85.3% with production of a 26.3% slurry. Thereactor effluent was thick and lumpy and reactor fouling forcedtermination of the run after 41/2 hours. The butyl rubber produced atthe steady state had an INOPO of 11.3 and an Mv=698,300 and Mp=660,000.It had a typical butyl molecular weight distribution with an Mz/Mw=1.7by GPC and less than 0.7% high ends.

In a run to produce butyl containing a branched high ends mode, run 3,KROl-K-Resin was dissolved in methyl chloride to yield a 2.51% solutionof the resin as one of the feeds to the reactor and a steady-state wasestablished with the following feeds into the reactor:

    ______________________________________                                        Isobutylene      52.38                                                        Isoprene         1.41                                                         Methyl Chloride  109.85                                                       KRO1-K-Resin     0.40                                                         AlCl.sub.3       0.048                                                                         164.09                                                       ______________________________________                                    

Reactor temperature was controlled at -93.5° C. and at the steady-statemonomer conversion was 94.8% with production of a 31.3% slurry. Thereactor effluent was a homogeneous fluid slurry and the reactor ran wellwith no evidence of fouling until the run was voluntarily terminated.The butyl rubber produced at the steady-state had an INOPO of 16.1 withan Mv=649,350 and Mp=600,000. The high INOPO reflects the presence inthe butyl of KROl-K-Resin which was attached to the butyl to yield ahigh ends branched fraction. None of the KROl-K-Resin was extractablefrom the butyl using MEK, a good solvent for KROl-K-Resin. TheKROl-K-Resin level in the reactor was 0.75% on monomers or about 0.79%on polymer. GPC/LALLS analyses showed this polymer to have a long highmolecular weight tail in the distribution. It had an Mz/Mw ratio of 3.9and contained no detectable amount of gel. Under these continuouspolymerization conditions, KROl-K-Resin introduced a branched high endsfraction of about 8.5% into butyl without producing gel while at thesame time acting as a slurry stabilizer to improve reactor operation byallowing operation at a high slurry concentration without fouling.

In another run to produce butyl containing a branched high ends modeusing KROl as the branching agent, run 4, a steady-state was establishedwith the following feeds into the reactor:

    ______________________________________                                        Isobutylene      54.235                                                       Isoprene         1.464                                                        Methyl Chloride  87.191                                                       KRO1-K-Resin     1.014                                                        AlCl.sub.3       0.061                                                                         143.97                                                       ______________________________________                                    

Reactor temperature was controlled at -92.0° C. At the steady-state,monomer conversion was about 99.5% with production of a 39.2% slurry.The reactor effluent was a very thick homogenous slurry and the reactorwas barely operable with -92° C. being the lowest polymerizationtemperature which could be maintained. The reactor only ran a few hoursbefore temperature control became impossible and more diluent had to beadded to dilute the slurry. The butyl rubber produced during thissteadystate had an INOPO of 17.3 with an Mv=433,350 and Mp=380,000. Thishigh INOPO for a feed with a B number of 2.70 is due to the KROl resinhaving become incorporated into the butyl to produce a branched highends fraction during polymerization. None of the KROl was extractablefrom the butyl using MEK as the extracting solvent. The KROl level inthe reactor was 1.82% on monomers or about 1.81% on polymer. The polymerapparently contained some very tenuous gel which was present in samplestaken directly from the reactor effluent and vacuum oven dried but wasabsent in the final recovered polymer which was kneaded in isopropylalcohol to effect deashing and was then hot mill dried. GPC analyses ofthe hot mill dried polymer showed the molecular weight distribution tobe bimodal with about 15.5% of the polymer present as a branched highmolecular weight mode with a molecular weight greater than 2.5 million.This polymer had an Mz/Mw ratio of 4.5 with no measurable amounts of gelin the hot mill dried material. Under these polymerization conditions,KROl resin effectively introduced a branched high ends mode into butylwithout producing objectionable gel while at the same time imp rovingreactor operation by acting as a slurry stabilizer.

In still another run to produce a butyl containing a branched high endsmode, run 5, KR03-K-Resin was dissolved in methyl chloride to yield a1.67% solution of the resin as one of the feeds to the pilot plantreactor and a steady-state was established with the following feeds intothe reactor:

    ______________________________________                                        Isobutylene      55.27                                                        Isoprene         1.53                                                         Methyl Chloride  99.51                                                        KRO3-K-Resin     0.73                                                         AlCl.sub.3       0.045                                                                         157.09                                                       ______________________________________                                    

Reactor temperature was controlled at -95° C. and at steady-stateconversion was 93% with production of 34.1% slurry. The reactor effluentwas a homogeneous fluid slurry, but gel was being made. Within a fewhours, the run had to be terminated as the reactor was badly fouled withgel. It could not be cleaned in the normal manner by warming and solventwashing because the fouling polymer was an insoluble gel. The reactorhad to be disassembled and manually cleaned before it could be usedagain. The butyl polymer produced during this steady-state conditioncontained more than 50% gel and so could not be characterized well; itcontained no extractable KR03. The KR03 level in the reactor for thisrun was 1.3% on monomers. It is clear that at that level and under thepolymerization conditions of this example, the KR03 was too reactive; itcaused more branching than desirable and resulted in formation of asignificant amount of gel. It should be noted that under the batchpolymerization conditions of Example 2, 2% KR03 on monomers did notresult in gel whereas under the continuous polymerization conditions ofthis example, 1.3% KR03 on monomers produced a highly gelled polymer. Ithas been found that under high conversion continuous polymerizationconditions, gel formation is more of a problem than under low conversionbatch polymerization conditions and gel formation is always more of aproblem when producing higher molecular weight polymers. It is thusnecessary to adjust the level and/or activity of the branching agent tosuit the polymerization conditions under which it is used in order toproduce the desired amount of high ends branching without producingundesirable amounts of gel.

In another run using KR03-K-Resin as the branching agent, run 6, theKR03 was partially hydrogenated prior to use in order to reduce itsactivity and avoid gel formation. Partial hydrogenation was effectedusing diisobutyl aluminum hydride as the reducing agent as alreadydescribed in Example 4. For this run, 50% of the unsaturation in thepolybutadiene blocks of the KR03 resin was removed by hydrogenation. Thepolystyrene blocks were not affected and the resin molecular weight alsoremained unchanged. The 50% chemically hydrogenated KR03 was dissolvedin methyl chloride to form a 2.06% solution of the partiallyhydrogenated run as one of the feeds to the pilot plant reactor and asteady state was established with the following feeds into the reactor:

    ______________________________________                                        Isobutylene        52.53                                                      Isoprene           1.43                                                       Methyl Chloride    92.58                                                      50% Chemically Hydro-                                                                            0.54                                                       genated KRO3                                                                  AlCl.sub.3         0.046                                                                         147.13                                                     ______________________________________                                    

Reactor temperature was controlled at -95° C. and the steady-stateconversion was about 99% with production of a 36.7% slurry. The reactoreffluent was a homogeneous, fluid, stable slurry and the reactor ranwell with no evidence of fouling until the run was terminatedvoluntarily. The butyl rubber produced during steady state had an INOPOof 24 with an Mv=200,000 and Mp=160,000. The high INOPO reflects thepresence of chemically bonded KR03 resin in the butyl. The KR03 level inthe reactor was 1% on monomers and it was all chemically bonded to thebutyl; none could be extracted from the recovered rubber. GPC/LALLSanalyses on this polymer showed the presence of about 11% of a highmolecular weight tail which was rich in the KR03 branched butyl. Thepolymer had an Mz/Mw ratio of 4.5. Under these polymerizationconditions, the 50% hydrogenated KR03 resin introduced a branched highends fraction into butyl without producing objectionable gel, while atthe same time improving reactor operation by acting as a slurrystabilizer. However, viscosity average and peak molecular weights werereduced.

It is possible to remove so much of the unsaturation in thepolybutadiene blocks of K-Resins that they become completely ineffectiveas branching agents. A KROl-K-Resin sample was chemically hydrogenatedusing diisobutyl aluminum hydride as in Example 4 to remove 85% of thepolybutadiene unsaturation. This resin identified as 85% HKROl wasdissolved in methyl chloride to yield a 1.90% wt. % solution of the 85%HKROl in methyl chloride as one of the feeds to the reactor. In run 7, asteady-state was achieved with the following feeds into the reactor:

    ______________________________________                                        Isobutylene      52.30                                                        Isoprene         1.42                                                         Methyl Chloride  89.60                                                        85% HKRO1        0.44                                                         AlCl.sub.3       0.034                                                                         143.80                                                       ______________________________________                                    

Reactor temperature was controlled at -95° C. and at the steady-statemonomer conversion was 98.0% with production of a 36.9% slurry. Thereactor effluent was a very fluid homogeneous slurry and the reactor ranwell with no evidence of fouling until the run was voluntarilyterminated. The butyl rubber being produced at the steady-state had anINOPO of 10.6 with an Mv=302,000 and Mp=280,000. This butyl had a nearlynormal INOPO for a feed with a B number=2.7 and essentially all of the85% HKROl resin was extractable by our MEK extraction procedure;essentially none of the resin had become bonded to the butyl duringpolymerization. GPC analyses showed this butyl to have a typicalmolecular weight distribution with an Mz/Mw ratio of 1.7 (based onGPC/LALLS) and less than 1% high ends. This result shows that removal ofmost of the active unsaturation in the KROl resin had rendered it quiteinert during continuous butyl polymerization conditions (just as it didunder the batch polymerization conditions of Example 4) and prevented itfrom acting as a branching agent to produce a controlled high endsfraction in butyl during polymerization. The 85% HKROl was still veryeffective as a slurry stabilizer to improve reactor operation, but itfunctions by adsorption on the butyl particles rather than by chemicalattachment during polymerization.

The continuous butyl polymerization experiments show thatstyrene-butadiene-styrene block copolymer resins can be used tointroduce a controlled high ends fraction into butyl duringpolymerization under conditions simulating commercial production. Thebranching activity of the styrene-butadiene-styrene block copolymerresins can be adjusted as desired by partial hydrogenation of thepolybutadiene block so that the desired degree of branching can beachieved without excessive gel formation. Selection of the resin, thedegree of hydrogenation, and the amount employed during polymerizationenable considerable control to be exercised over the amount and natureof the high ends fraction introduced into butyl during polymerization.Styrenebutadiene block copolymers combine the desirable attributes ofproducing high ends branching while at the same time acting as slurrystabilizers to improve reactor operation and reduce the extent and rateof reactor fouling. It is thus possible to produce the desired high endsfraction under practical conditions by eliminating fouling of thereactor with insoluble gel. The slurry stabilization effectiveness ofthe block copolymers is enhanced by hydrogenation so activity inbranching can be adjusted by partial hydrogenation without impairingtheir effectiveness at improving reactor operation.

While the continuous polymerization experiments utilized severalstyrene-butadiene-styrene block copolymer resins, other branching agentsand slurry stabilizers can be employed to accomplish the same end whilestill employing partial hydrogenation to adjust branching activity tothe desired level. As discussed earlier, it is most preferable tocombine the function of branching agent and slurry stabilizer in onespecies by utilizing a block copolymer comprising a lyophilic or methylchloride soluble block (e.g., polystyrene, polyvinylchloride) and ablock containing multiple reactive unsaturation (e.g., a polydieneblock) to produce the desired high ends branched fraction duringpolymerization. Suitable block copolymers include: styrene/butadiene,styrene/isoprene, styrene/piperylene, etc. The preferred blockarchitecture is a star block with the lyophile block on the periphery.It is also possible, though less preferable, to use separate species toaccomplish the function of branching as already discussed with orwithout additional reagents for slurry stabilization.

EXAMPLE 6

In order to more fully demonstrate the advantages of the improved butylswith controlled high ends branched fraction of this invention, a morecomplete evaluation of several polymers prepared in the continuouspolymerization unit was undertaken in comparison with commercial gradesof butyl rubber. Also included in the comparison is a butyl compositionprepared by blending. The improved butyls with controlled high endsbranched fraction selected for evaluation were prepared in thecontinuous polymerization unit in runs similar to those described inExample 5 using KROl-K-Resin as the branching agent and slurrystabilizer.

The high ends branched butyl polymer designated R49-C12 was preparedwith the following feeds into the reactor:

    ______________________________________                                        Isobutylene      35.122                                                       Isoprene         0.878                                                        Methyl Chloride  114.822                                                      KRO1-K-Resin     0.612                                                        AlCl.sub.3       0.050                                                                         151.5                                                        ______________________________________                                    

Reactor temperature was controlled at -94.2° C. and at the steady-statemonomer conversion was 89.7% with production of a 21.7% slurry. The KROllevel was 1.7 wt. % on monomers or 1.9 wt. % on polymer and none wasextractable from the recovered butyl. The reactor ran well and the butylproduced was gel free after hot milling and contained approximately20.5% branched high ends mode which was rich in the K-Resin asdetermined by GPC.

Both the Refractive Index (RI) and Ultraviolet (UV) traces showedbimodality in the molecular weight distribution with the UV traceconfirming the high concentration of the K-Resin in the high molecularweight branched mode. The Mz/Mw ratio by GPC (LALLS) was 5.6. Othercharacterizations and evaluations on this polymer are given later inthis example.

The high ends branched butyl polymer designated R4-C9 was prepared withthe following feeds into the reactor:

    ______________________________________                                        Isobutylene      48.44                                                        Isoprene         1.46                                                         Methyl Chloride  121.24                                                       KRO1-K-Resin     0.409                                                        AlCl.sub.3       0.053                                                                         171.6                                                        ______________________________________                                    

Reactor temperature was controlled at -93° C. and at steady-statemonomer conversion was 91.0% with production of a 26.7% slurry. The KROllevel was 0.82 wt. % on monomers or 0.90 wt. % on polymer and none wasextractable from the recovered butyl which was gel free after hotmilling and contained about 12.5% branched high ends mode rich inK-Resin as determined by GPC.

For this polymer the high ends branched mode appeared as a bump in theRI trace because the peak molecular weight of the lower mode wasrelatively high and both modes were fairly broad so that they overlappedconsiderably and were not resolved. However, the high molecular weightbranched mode which is rich in K-Resin was again clearly evident in theUV trace. The Mz/Mw ratio of this polymer by GPC (LALLS) was 9.0. Othercharacterizations and evaluations are given later in this example.

The commercial polymers included as controls in the evaluation wereButyl 365 and Butyl 268 (described previously). Also included in theevaluation was a blend polymer prepared by solution blending of Butyl365, high molecular weight polyisobutylene (Vistanex L140), and a lowermolecular weight higher unsaturation butyl with an Mv=200,000 preparedin the continuous polymerization unit. GPC analyses of all of thesepolymers are summarized in the following table (molecular weightvalues×10⁻ 3):

    ______________________________________                                                                             4Mp,                                                                          High                                             LALLS      IR                Ends,                                    Sample    Mw      Mz/Mw    Mw   Mp   Mp(a) wt. %                              ______________________________________                                        Butyl 268 521     1.7      507  500  (b)   0.7                                Butyl 365 375     1.8      406  308  (b)   2.0                                Blend B (Ex. 1)                                                                         547     2.6      498  310  (b)   9.0                                R49C12    1530    5.6      476  292  1500  20                                 R4C9      1580    9.0      454  350  1400  12                                 ______________________________________                                         (a) = UV measurement                                                          (b) = same as peak using RI                                              

The model blend has a higher Mz/Mw than the reference commercialsamples, but not nearly so high as is achieved with the controlled highends branching produced by KROl-K-Resin; there are limitations inblending linear components. The two polymers R49C12 and R4C9 each had aclearly resolved branched high ends mode with a very high Mp for thehigh ends mode. FIGS. 2 and 3 contrast a GPC chromatogram (RI) for atypical Butyl 268 polymer and a polymer such as R49C12 which contains abranched high ends mode. The strong U.V. absorption peak by thepolystyrene lyophile indicates incorporation of the branching agent inthe high molecular weight end as indicated in the table (FIG. 4illustrates such a U.V. trace).

The Mooney viscosity, green strength, and stress-relaxation measurementson the polymers of this example are summarized (for neat polymer) in thefollowing table:

    ______________________________________                                                             Tensile  4-Minute                                                   Mooney    Green    Relaxed                                                    (ML 1 + 8 Strength Stress                                                     at 125° C.)                                                                      (psi)    (psi)                                           ______________________________________                                        Exxon Butyl 268                                                                            50          33.8     11.8                                        Exxon Butyl 365                                                                            33          28.1     7.3                                         Blend        37          32.1     9.7                                         R49C12       42          33.1     9.5                                         R4C9         50          35.1     11.1                                        ______________________________________                                    

The higher molecular weight Butyl 268 has higher green strength, but atthe expense of longer relaxation time as shown by the higher relaxedstress after 4-minutes relaxation time. The green strength of Butyl 268is adequate for most purposes, but it would be highly desirable toachieve this at the lower Mooney viscosity and higher stress-relaxationrate of Butyl 365. The blend is an improvement in that direction--itachieves a higher green strength than Butyl 365 and improved relaxationstress compared to Butyl 268. The high ends branched polymer R49C12shows a higher green strength and faster stress-relaxation time than theblend; while R4C9 shows a much higher green strength than even Butyl 268at a lower relaxed stress.

The polymers of this example were each compounded in a typical butylrubber innertube formulation for further evaluation. The formulationused is shown below (parts by weight):

    ______________________________________                                        Polymer              100                                                      GPF Carbon Black (Grade N660)                                                                      70                                                       Paraffinic rubber process oil.sup.(a)                                                              25                                                       Stearic Acid          1                                                       ______________________________________                                    

The formulations were prepared using a conventional laboratory internalmixer (Banbury®) and mix cycle. Mooney viscosity, green strength, andstress-relaxation measurements on the compounded polymers are summarizedin the following table.

    ______________________________________                                                 Polymer Compound  Tensile  4-Minute                                           Mooney  Mooney    Green    Relaxed                                            (ML 1 + 8                                                                             (ML 1 + 4 Strength Stress                                             at 125° C.)                                                                    at 100° C.)                                                                      (psi)    (psi)                                     ______________________________________                                        Butyl 268  50          38.5    24.8   3.54                                    Butyl 365  33        30        19.8   1.88                                    Blend B (Ex. 1)                                                                          37          34.5    24.1   2.64                                    R49C12     42        30        25.6   1.63                                    R4C9       50        39        28.3   3.30                                    ______________________________________                                    

Results are similar to the neat polymer results, and the advantages ofthe controlled high ends branched polymers are evident. The commercialbutyl polymers show the expected results with the model blend being astep toward achieving a better balance of properties. The controlledhigh ends branched polymers significantly altered the balance ofproperties. In this innertube formulation, R4C9 had much higher greenstrength than Butyl 268 and a lower relaxed stress. R49C12 had acompounded Mooney viscosity equivalent to Butyl 365 with a greenstrength better than Butyl 268 and a relaxed stress lower than Butyl365; a particularly desirable combination of properties.

To complete the evaluation, vulcanizate properties were measured on theinnertube formulations with the following results:

    __________________________________________________________________________    Vulcanizate Properties (Innertube Formulation).sup.(a)                                         Stress-Strain Properties.sup.(c)                             Monsanto Rheometer.sup.(b)                                                                     100%                                                                              300%                                                                              Tensile  Hard-                                       Delta    TS2 TC90                                                                              MOD MOD Strength                                                                           Elong.                                                                            ness                                        Torque   (Min)                                                                             (Min)                                                                             (MPa)                                                                             (MPa)                                                                             (MPa)                                                                              (%) (Shore A)                                   __________________________________________________________________________    Butyl 268                                                                          39.8                                                                              5.6 26.8                                                                              1.5 5.4 11.3 590 54                                          Butyl 365                                                                          49.8                                                                              4.5 26.1                                                                              2.2 6.9 10.0 430 58                                          Blend B                                                                            34.0                                                                              5.4 28.3                                                                              1.8 5.9 10.6 560 58                                          R49C12                                                                             45.4                                                                              5.0 26.8                                                                              2.1 7.9 11.4 440 64                                          R4C9 49.5                                                                              4.5 26.3                                                                              2.3 7.7 11.1 430 60                                          __________________________________________________________________________     .sup.(a) Cure system (parts by weight): Zinc oxide  5, Sulfur  2.0,           mercaptobenzothiazole  0.5, tetramethyl thiuram disulfide  1.5                .sup.(b) 3° Arc, 1.7 Hz, 160° C. Delta torque = change in       torque from minimum to maximum; TS2 = time to 2 unit rise above minimum;      TC90 = optimum cure time (90% of delta torque)                                .sup.(c) Samples cured 30 minutes at 150° C.                      

The controlled high ends branched polymers yielded a high cure state asshown by high delta Torque in the Monsanto Rheometer and high modulusalong with good tensile strength and elongation. Blend B had a lowercure state as indicated by the low delta Torque in the rheometer due tothe unvulcanizable polyisobutylene component (Vistanex L140), whichmakes up the higher molecular weight species in this blend.

EXAMPLE 7

A multifunctional lyophile-containing reagent was prepared byhydrochlorination of a styrene-isoprene-styrene triblock polymercontaining a very short central polyisoprene block. The triblock polymerwas polymerized anionically using sec-BuLi as the catalyst incyclohexane with 10% THF. Monomer was added sequentially (styrene,isoprene, and then styrene again) to form the triblock. The centralpolyisoprene block comprised 5.78 wt. % of the triblock polymer. It wasfunctionalized by addition of HCl to the central isoprene block inmethylene chloride solution at 0° C. The functionalized polymercontained 0.6 wt. % chlorine attached to the short central polyisopreneblock; total Mn of the the triblock polymer was about 200,000. Thefunctionalized triblock polymer was readily soluble in methyl chloridebecause of its high polystyrene content and essentially constituted alyophile highly functionalized in the center by virtue of the chlorineatoms on the short central polyisoprene block. Each triblock chaincontained greater than 25 active chlorine atoms to serve as sites forattaching butyl chains during polymerization to form the high ends mode.Because of the anionic polymerization conditions used (10% THF present),the isoprene was largely incorporated in the 3,4 mode in the centralpolyisoprene block and the HCl adduct contained mostly pendant tertiarychlorine atoms which are highly active during cationic butylpolymerization conditions. The structure of the active tertiary chlorinefunctionality is shown below: ##STR4##

Under cationic butyl polymerization conditions the tertiary chlorine isremoved to form a tertiary carbenium ion which initiates a butyl chainso that the butyl chain is attached to the functionalized lyophile atthe site where the tertiary chlorine atom was removed. Themultifunctional lyophile of this example is identified as 9851-39-D.

This reagent was used in a batch dry box polymerization to produce abutyl rubber containing a high ends mode.

A 500 ml. reaction flask fitted with a thermometer, stirrer, anddropping funnel was set up in a glove box having an oxygen andmoisture-free nitrogen atmosphere and the flask was cooled to -65° C. byimmersion in a controlled temperature liquid-nitrogen-cooled heattransfer bath. The reactor was charged with 409.75 g. purified drymethyl chloride and then 0.25 g. 9851-39-D was added as a dry powder andstirred in. It dissolved quickly to give a clear solution. Then 48.5 g.purified, dried, and distilled polymerization grade isobutylene and 1.5g. purified, dried and distilled polymerization grade isoprene and wereadded and stirred in to give a feed batch blend containing 10.9% of aB-3 feed with 0.5% 9851-39-D on monomers. Nine ml. of a catalystsolution consisting of 0.3 wt. % ethyl aluminum dichloride in methylchloride was dripped in slowly over the course of 8 minutes whilestirring and maintaining temperature by immersion of the reactor in theheat transfer bath. The reactor was then quenched by addition of coldmethyl isobutyl ketone, MIBK (25 ml.) and transferred to the hood whereit was allowed to stir and warm slowly with additional MIBK being addedas the methyl chloride and unreacted monomers flashed off to yield afine dispersion of polymer in MIBK at room temperature. The polymer wasrecovered by settling and decanting off the MIBK and then reslurrying infresh MIBK and settling and decanting again to try to extract anyunreacted functional lyophile from the butyl polymer. The extractedbutyl was kneaded and washed in isopropanol to remove catalyst residuesand then vacuum oven dried at 80° C. with 0.2 wt. % BHT mixed into it asan antioxidant. The MIBK extracts were combined and allowed to evaporateto concentrate and then precipitated in methanol; however, essentiallyno polymer was present in the MIBK extracts, all the 9851-39-D hadbecome incorporated into the butyl during polymerization and wasrecovered with the butyl. Thirty-five and a half grams of white, tough,rubbery butyl rubber were recovered. Conversion was 80% with a catalystefficiency of 1500 g/g. The recovered polymer had a viscosity averagemolecular weight of 230,000 with an INOPO of 8.

GPC analysis using RI and UV detectors showed the polymer to be bimodalwith essentially all of the polystyrene lyophile in the high molecularweight mode as shown by the UV detector. The main polymer mode had apeak molecular weight of 140,000 and a normal breadth for batch butylpolymerization, but a second high molecular weight mode with a peakmolecular weight of greater than 3 million (uncorrected) containing allof the polystyrene with many butyl arms attached was also present. Useof the multifunctional lyophile permitted the formation of a highmolecular weight mode during polymerization. A large number of the butylchains formed during polymerization were attached to eachmultifunctional lyophile molecule to form the high ends mode. Althoughonly 0.5% of the functional polystyrene based on monomers was added tothe polymerization, approximately 11% of the butyl became incorporatedinto the high ends mode because so many (i.e., approx. 25) butyl chainsbecame attached to each multifunctional polystyrene. The amount of thehigh ends mode can readily be varied by varying the amount of themultifunctional lyophile added to the polymerization; the molecularweight of the high ends mode is readily controlled by varying thefunctionality of the multifunctional lyophile and thus the number ofbutyl chains formed during polymerization which become linked togetherby virtue of being attached to the same lyophile molecule. This approachthen affords a practical way of controlling both the molecular weightand amount of the high ends mode produced. Other molecular weightcharacteristics of the modified polymer were: Mn 99,000; Mw=550,000;Mw/Mn=5.55; Mz/Mw (LALLS)=greater than 9.

EXAMPLE 8

A multifunctional lyophile-containing reagent was prepared byhydrochlorination of a styrene-isoprene-styrene triblock polymercontaining a short central polyisoprene block. In this example, thelyophile was prepared by "living" anionic polymerization of styrene incyclohexane at 60° C. with sec-BuLi catalyst; after completion of thestyrene polymerization a small amount of isoprene was added as a cappingagent and then the capped polymer was coupled with ethyl benzoate togive triblock polymer with a very short central polyisoprene block. Thecoupled triblock polymer had a molecular weight of 170,000 with an INOPOof 5.6 and contained about 1.3 wt. % isoprene as a central blockattached to the coupling agent. It was functionalized by addition of HClin methylene chloride at approximately 3° C. The functionalized polymercontained 0.39 wt. % chlorine mostly present as the tertiary chloride,as in Example 7. The functionalized lyophile contained about 20 activechlorine atoms per chain, again clustered in the short centralpolyisoprene portion. This polyfunctional lyophile was identified as10564-48-6. It was used in a batch dry box polymerization to produce abutyl rubber containing a high ends mode.

A batch butyl polymerization was conducted as in Example 7 except that0.25 g. 10564-48-6 was dissolved in the methyl chloride as thepolyfunctional lyophile instead of 9851-39-D. In this batch run, 71/4ml. of 0.3% EADC in methyl chloride catalyst was dripped in over thecourse of 10 minutes while maintaining reactor temperature between -64°and -62° C. 11.7 g. of tough, rubbery butyl rubber were recovered as inExample 7. The rubber had a viscosity, average molecular weight of286,000 and an INOPO of 9.1. GPC analysis showed this polymer was alsobimodal containing a high ends mode consisting of many butyl chainsattached to the polyfunctional lyophile. In this example the main modehad a peak molecular weight of 180,000, and the high ends mode a peak(uncorrected) of greater than 4.5 million. Again, the polyfunctionallyophile permitted production during polymerization of a butyl rubbercontaining a high ends mode. The amount and molecular weight of thishigh ends mode is controllable by varying the amount and functionalityof the polyfunctional lyophile. Other molecular weight characteristicsof the modified polymer were: Mn=160,000; Mw=810,000; Mw/Mn=5.08; Mz/Mw(LALLS)=greater than 9; estimated fraction of polymer in high molecularweight fraction=21%.

EXAMPLE 9

Several multifunctional lyophile-containing reagents were prepared byhydrochlorination of a series of random styrene/isoprene copolymersprepared by radical polymerization of styrene/isoprene feeds in tolueneusing azo-bis-isobutyronitrile (AZBN) initiator at 80° C. Thesemultifunctional lyophiles were used in batch polymerization as inExample 7 to prepare butyl rubbers containing a high ends mode. Theamount and molecular weight of the high ends mode was controllable byvarying the amount and functionality of the multifunctional lyophile;Tables 9-1 and 9-2 below summarize the experimental results. It can beseen that useful polymers can be produced and that gel can result if anexcessive amount of cationically active functionality is present in thebranching agent.

                  TABLE 9-1                                                       ______________________________________                                        HCSI Branching Agent.sup.(a)                                                  Run     Isoprene.sup.(b)                                                                        Chlorine.sup.(b)                                                                          Mv.sup.(c)                                                                         Cl/Chain.sup.(d)                           ______________________________________                                        1       0.32      0.14        125  20                                         2       0.32      0.14        125  20                                         3       0.52      0.24         85  25                                         4       0.66      0.33         60  25                                         5       0.66      0.33         60  25                                         6       1.0       0.93        135  150                                        ______________________________________                                         .sup.(a) Hydrochlorinated styrene/isoprene radical copolymer.                 .sup.(b) Weight %.                                                            .sup.(c) Values shown are × 10.sup.-3.                                  .sup.(d) Approximate number of chlorine atoms per chain.                 

                  TABLE 9-2                                                       ______________________________________                                        Polymerizations Using HCSI Branching Agent                                            Agent.sup.(a)              High Ends                                  Run     Conc     Mp.sup.(b)                                                                              Mz/Mw.sup.(c)                                                                         Fraction.sup.(d)                           ______________________________________                                        1       0.5      280       3.5      8.0                                       2       1.0      250       4.9     15.5                                       3        0.75    300       3.5     12.5                                       4       0.5      320       3.5      8.5                                       5       1.0      150       6.0     16.5                                       6       1.0      GEL - NO GPC                                                                  RESULTS                                                      ______________________________________                                         .sup.(a) Weight percent based on monomers                                     .sup.(b) Values shown are × 10.sup.-3                                   .sup.(c) Using LALLS/GPC technique                                            .sup.(d) Weight percent polymer equal to and greated than 4Mp; separate       highends mode with peak MW greated than 2.5 × 10.sup.6.            

EXAMPLE 10

A series of multifunctional lyophile-containing reagents were preparedby chlorination under radical conditions of a series of commercial andradically polymerized polystyrenes. The polystyrenes were chlorinated inmethylene chloride using in situ formed t-butyl hypochlorite as thechlorinating agent. The in situ t-butyl hydrochlorite was formed bybubbling chlorine gas into a methylene chloride solution of thepolystyrene containing t-butyl alcohol plus some aqueous NaOH. Underthese conditions some benzylic chlorines, which are active undercationic polymerization conditions and serve as sites for attachingbutyl chains, are introduced into the polystyrene. The active benzylicchlorines introduced are shown below: ##STR5##

Other less active chlorines are also introduced into the polystyreneblock under these conditions so that the branching reagent can besynthesized to contain a higher concentration of chlorine before its useresults in a gelled polymer. The multifunctional lyophiles so preparedwere used in batch butyl polymerization as in Example 9 to prepare butylrubbers containing a high ends mode. The amount and molecular weight ofthe high ends mode was controlled by varying the amount andfunctionality of the multifunctional lyophile; Table 10-1 belowsummarizes the experimental results.

                  TABLE 10-1                                                      ______________________________________                                        CPS Branching Agent.sup.(a)                                                                                               High                                                        Agent             Ends                                   Cl     Mv     Cl/Chain                                                                             Conc. Mp   Mz/Mw  Fraction                          Run  (b)    (c)    (d)    (e)   (c)  (f)    (g)                               ______________________________________                                        1    1.99   285    100    0.5   300  3.0     6.1                              2    1.99   285    100    1.0   150  5.0    11.5                              3    0.37   265    15     1.0   300  2.4    4                                 4    0.37   265    15     2.0   250  3.5    8                                 5    10.48  221    300    0.5   250  3.5     6.2                              6    10.48  221    300    1.0   180  6.0    12.5                              7    0.84   468    50     0.5   280  3.5     7.5                              8    0.84   468    50     1.0   240  6.0    14.5                              9    6.48    79    75     0.5   300  3.0     6.2                              10   6.48    79    75     1.0   180  5.5    12.5                              ______________________________________                                         .sup.(a) Radical Chlorinated Polystyrene                                      (b) Weight percent                                                            (c) Values shown are × 10.sup.-3                                        (d) Approximate number of chlorine atoms per chain                            (e) Weight percent based on monomer                                           (f) LALLS/GPC technique                                                       (g) Weight percent polymer equal to and greater than 4Mp; separate high       ends mode except for runs 3,4 with broadened distribution. High ends peak     Mw greated than 2 × 10.sup.6 ; runs 7, 8 greated than 3 ×         10.sup.6                                                                 

The use of multifunctional lyophile-containing reagents of the typedescribed in Examples 7-10 to introduce a controlled high ends mode intobutyl rubber during polymerization is particularly desirable undercontinuous polymerization conditions because it introduces the desiredhigh ends mode in a controllable manner without the associated problemof fouling the reactor with insoluble gel which prevents washing thereactor. Additionally, the multifunctional lyophile acts as a slurrystabilizer to prevent reactor fouling and so is a particularly desirableway of introducing the high ends mode.

EXAMPLE 11

Several polymers of the present invention were tested for green strengthusing the test method previously described as the stress relaxationprocessability tester (SRPT). Testing was conducted at 30° C. andmeasurements were made at 75% relaxation for polymers, 50% for blends.Two groups of polymers and blends were tested, unhalogenated andbrominated. For the first group of unhalogenated compositions,comparative polymers included butyl rubber grade 268 and grade 365 aspreviously described. The data was normalized using the results forButyl 268 as the reference, with the data for the comparative polymersestablishing a reference line (FIG. 5). The blend and directlypolymerized polymers had green strength and relaxation time values thatgenerally exceeded this reference line. Several of the samples testedwere produced in a large scale polymerization plant and average valuesrepresenting three samples each are shown. It can be seen that, comparedwith the reference polymer, the improved composition of this inventionhas a faster relaxation time at a given green strength and, conversely,a higher green strength for a given relaxation time. Preferably theimproved compositions have at least about a 5% improvement, ascharacterized by stress relaxation, more preferably at least about 10%,most preferably at least about 15%, for example, a 20% improvement. Ascan be seen from FIGS. 5 and 6 (as discussed below) the rate of changeof green strength improvements differs from that of stress relaxation.At constant stress relaxation the preferred improvement in greenstrength would be approximately one-half of the values just recited,i.e., preferably at least about a 2.5% improvement, etc. The referencepolymer, as described in detail in previous examples, is a substantiallylinear polymer in its molecular configuration and does not contain thedesirable high ends fraction which can also be achieved through blending(as, for example, where essentially linear components are used toprepare the blend).

Similar results are obtained where the polymer composition of thepresent invention is a halogenated polymer, e.g., brominated. Polymersof this type were prepared and compared, as above, using a brominatedbutyl reference polymer, grade 2222 (Mooney viscosity, 1+8 at 125° C.=32±5, typical bromine content, 2 wt. %). In addition, another commercialpolymer was used for comparative purposes to establish a reference linefor substantially linear polymers, brominated butyl grade 2233 (Mooneyviscosity, 1+8 at 125° C.=37±5, typical bromine content, 2 wt. %). Thedata are shown in FIG. 6; the data point for the large scale plantrepresents an average of six individual samples.

What is claimed is:
 1. A process for producing a composition of mattercomprising a C₄ to C₇ isoolefin homopolymer rubber, butyl copolymerrubber, or mixtures thereof, wherein the molecular weight distributionof said rubber or said mixture is such that the ratio of the moment ofsaid molecular weight distribution, Mz/Mw, is equal to 2.0 to about 11.0and that portion of said molecular weight distribution which is equal toor greater than 4 times the peak molecular weight, Mp comprises fromabout 8 to about 25 weight percent of the total polymer species, Mp isabout 250,00 to about 850,000 and wherein said polymer species ofmolecular weight less than Mp are substantially branch free, saidprocess comprising the step of polymerizing a C₄ to C₇ isoolefin, or amixture of a C₄ to C₇ isoolefin and a C₄ to C₁₄ conjugated diene, andincorporating an effective amount of a cationically functional reagentduring said polymerizing step, at conditions such that substantially allof said cationically functional reagent is grafted to said polymer. 2.The process of claim 1 wherein said functional reagent is present duringpolymerization at a concentration of about 0.3 to about 3.0% by weight,based on the weight of monomers to be polymerized.
 3. The process ofclaim 2 wherein said butyl rubber comprises cationically polymerizedcopolymers of C₄ -C₇ isoolefins and C₄ -C₁₄ conjugated dienes whichcomprise about 0.5 to about 15 mole percent of said diene and about 85to about 99.5 mole percent of said isoolefin.
 4. The process of claim 1wherein said rubber is substantially gel free.
 5. The process of claim 1wherein said cationically functional reagent comprises cationicallyactive halogen or cationically active unsaturation.
 6. The process ofclaim 5 wherein said cationically active unsaturation comprises apolydiene and partially hydrogenated polydiene selected from the groupconsisting of polybutadiene, polyisoprene, polypiperylene, naturalrubber, styrene-butadiene rubber, ethylene-propylene diene monomerrubber, styrene-butadiene-styrene and styrene-isoprene-styrene blockcopolymers.
 7. The process of claim 1 wherein said reagent furthercomprises a lyophilic, polymerization diluent soluble portion.
 8. Theprocess of claim 1 comprising conducting said polymerization in adiluent in which said rubber is soluble.
 9. The process of claim 8 inwhich said diluent is selected from the group consisting of aliphatichydrocarbons and aliphatic hydrocarbons blended with methyl chloride,methylene chloride, vinyl chloride or ethyl chloride.
 10. The process ofclaim 1 wherein said functional reagent is capable of stabilizing thepolymerized rubber product produced as a slurry.
 11. The process ofclaim 10 wherein said functional reagent is a multifunctional lyophile.12. The process of claim 11 wherein said multifunctional lyophilecomprises polystyrene comprising cationically active halogenfunctionality.
 13. The process of claim 12 wherein said multifunctionallyophile comprises a hydrohalogenated styrene-isoprene-styrene triblockpolymer.
 14. The process of claim 13 wherein said triblock polymer has anumber average molecular weight of about 100,000 to about 300,000, thecentral polyisoprene block prior to hydrohalogenation comprises about 1to about 10 weight percent of said triblock polymer and followinghydrohalogenation contains about 0.1 to about 1.0 weight percenthalogen.
 15. The process of claim 11 wherein there is present duringpolymerization about 0.3 to about 3.0 weight percent of saidmultifunctional lyophile based on the monomers to be polymerized. 16.The process of claim 3 wherein said butyl rubber is isobutylene-isoprenerubber.
 17. The process of claim 1, wherein said polymerizing step isconducted in two or more polymerization zones.
 18. The process of claim17 wherein said zones are present in a single polymerization vessel. 19.The process of claim 17 wherein said zones are present in two or morepolymerization reactors operating in parallel or series.